Low goitre prevalence among users of oral contraceptives in a population sample of 3712 women

OBJECTIVE

Goitre occurs primarily in women. As oestrogens may be an aetiologic factor, the use of oral contraceptives (OC) could be associated with an increased risk of goitre. This is supported by experimental data, but a recent population study suggested decreased thyroid volumes among users of OC.

DESIGN

Cross-sectional, observational study.

PARTICIPANTS

A random population sample of 3712 women from two Danish cities.

MEASUREMENTS

Ultrasound and clinical examination of the thyroid, measurement of serum TSH, T3, T4 and thyroglobulin, and personal interviews with registration of use of OC or post-menopausal oestrogen therapy. Data were analysed in linear models and logistic regression adjusting for age and iodine status.

RESULTS

Thyroid volume was lower among users than non-users of OC, 11.1 ml vs. 12.1 ml (P < 0.001). Use of OC was correspondingly associated with a reduced prevalence of thyroid enlargement on ultrasound (odds ratio 0.53, 95% confidence interval 0.37-0.74) and of palpable and visible goitre (OR 0.24, 95% CI 0.07-0.81). Serum TSH was 1.24 mU/l in non-users of OC and 1.35 mU/l in users (P = 0.002). The percentage of goitre cases prevented by OC compared to a hypothetical population without use of OC was 29%. Post-menopausal oestrogen therapy showed similar, but statistically non-significant, associations.

CONCLUSION

Use of oral contraceptives was associated with a lower thyroid volume and reduced risk of goitre, and clinically evident goitre was four times more frequent among non-users than among users of oral contraceptives.

Use of dietary supplements in Denmark is associated with health and former smoking

OBJECTIVES

To describe the use of dietary supplements in a group of Danish adults and to investigate the differences between users and non-users with respect to age, gender, health and lifestyle factors.

DESIGN

Cross-sectional study in two Danish cities.

SETTING

The Danish Investigation on Iodine Intake and Thyroid Diseases, 1997-1998.

SUBJECTS

Participants were 3707 women (selected age groups between 18 and 65 years) and 942 men (60-65 years). Participation rate was 50%. Supplement data were collected in a personal interview. Data on education, smoking, alcohol intake, physical activity, use of medication and self-perceived health were derived from a self-administered questionnaire. Multiple logistic regression was used for the statistical analysis.

RESULTS

Participants were asked about all kinds of supplements, ranging from products containing vitamins and minerals, to fish oils and products of herbal origin. On average 59% reported use of some kind of dietary supplement. Most common were combined multivitamin/mineral products (48%) followed by single vitamin C products (10%). Twelve per cent used three or more different supplements. Supplement use was strongly associated with age and gender, being highest among elderly women (78%). Ex-smokers were more likely to use supplements than subjects who had never smoked (odds ratio (OR) 1.36, 95% confidence interval (CI) 1.09-1.76). Supplement use was more likely among subjects who had many days of illness 95% CI 1.12-1.66) and among users of medication 95% CI 1.04-1.42). Subjects who perceived their health as poor were more likely to use supplements other than just a multivitamin/mineral tablet 95% CI 1.31-3.77).

CONCLUSIONS

Use of dietary supplements was related to age, gender and smoking, but also to poor self-perceived health status and absence from work. This indicates that a group of people use supplements as a form of self-medication.

Narrow individual variations in serum T(4) and T(3) in normal subjects: a clue to the understanding of subclinical thyroid disease

High individuality causes laboratory reference ranges to be insensitive to changes in test results that are significant for the individual. We undertook a longitudinal study of variation in thyroid function tests in 16 healthy men with monthly sampling for 12 months using standard procedures. We measured serum T(4), T(3), free T(4) index, and TSH. All individuals had different variations of thyroid function tests (P < 0.001 for all variables) around individual mean values (set points) (P < 0.001 for all variables). The width of the individual 95% confidence intervals were approximately half that of the group for all variables. Accordingly, the index of individuality was low: T(4) = 0.58; T(3) = 0.54; free T(4) index = 0.59; TSH = 0.49. One test result described the individual set point with a precision of +/- 25% for T(4), T(3), free T(4) index, and +/- 50% for TSH. The differences required to be 95% confident of significant changes in repeated testing were (average, range): T(4) = 28, 11-62 nmol/liter; T(3) = 0.55, 0.3--0.9 nmol/liter; free T4 index = 33, 15-61 nmol/liter; TSH = 0.75, 0.2-1.6 mU/liter. Our data indicate that each individual had a unique thyroid function. The individual reference ranges for test results were narrow, compared with group reference ranges used to develop laboratory reference ranges. Accordingly, a test result within laboratory reference limits is not necessarily normal for an individual. Because serum TSH responds with logarithmically amplified variation to minor changes in serum T(4) and T(3), abnormal serum TSH may indicate that serum T(4) and T(3) are not normal for an individual. A condition with abnormal serum TSH but with serum T(4) and T(3) within laboratory reference ranges is labeled subclinical thyroid disease. Our data indicate that the distinction between subclinical and overt thyroid disease (abnormal serum TSH and abnormal T(4) and/or T(3)) is somewhat arbitrary. For the same degree of thyroid function abnormality, the diagnosis depends to a considerable extent on the position of the patient's normal set point for T(4) and T(3) within the laboratory reference range.

Surveyance of disease frequency in a population by linkage to diagnostic laboratory databases. A system for monitoring the incidences of hyper- and hypothyroidism as part of the Danish iodine supplementation program

In Denmark an increase in iodine intake through salt iodization has been introduced in 1998. In parallel a program for surveyance of thyroid diseases in the population was developed as recommended by UNICEF and WHO.

OBJECTIVE

To develop and evaluate a computer based system to identify and register new cases of hyper- and hypothyroidism in a well defined cohort, by linkage to diagnostic laboratory databases.

DESIGN AND RESULTS

(1) Two sub cohorts for monitoring were defined (n=535,859), and evaluated to minimize loss of new cases. Collaboration was established with laboratories covering thyroid hormone analyses in the cohort; (2) a diagnostic algorithm was defined and evaluated against clinical practice; (3) evaluation of the laboratory methods employed by the four participating laboratories, to ensure they would reach the same diagnosis in a patient; (4) a register database was developed which used data imported from the laboratory databases to automatically identify previously unknown cases of hyper- and hypothyroidism and record diagnostic activity in the area. All parts of the registration were carefully evaluated.

CONCLUSION

We describe for the first time a computer based system for prospective measuring the incidence rate of hyper- and hypothyroidism. The system is particularly useful for monitoring of iodine supplementation programmes.

Association of tobacco smoking with goiter in a low-iodine-intake area

BACKGROUND

Goiter development depends on genetic and environmental factors. The major environmental factor is iodine intake, whereas diverging results have been published concerning the association between smoking and goiter.

METHODS

A comparable, cross-sectional study was performed of patients from 2 areas in Denmark with mild and moderate iodine deficiency. A random sample of women and men in selected age groups from the general community was investigated; 4649 subjects participated. Smoking habits were investigated with questionnaires and interviews. Ultrasonography and clinical examination of the thyroid were performed, serum thyroglobulin was measured, and iodine concentration in spot urine samples was analyzed. Data were analyzed in linear models and logistic regression analyses.

RESULTS

Serum thyroglobulin level and thyroid volume at ultrasonography were positively associated with smoking habits (P<.001); the association was stronger in the area with the lowest iodine intake (interaction: P<.001 for thyroglobulin, P =.04 for thyroid volume). A positive association with smoking was also found for thyroid enlargement (odds ratio, 2.9; 95% confidence interval, 2.2-3.7) and palpable goiter (odds ratio, 3.1; 95% confidence interval, 1.6-5.8). Ex-smokers had a goiter prevalence close to that of never smokers. The fraction of goiter cases attributable to smoking was 49% (95% confidence interval, 29%-65%).

CONCLUSIONS

Thyroid volume and goiter prevalence were closely associated with smoking habits, with the strongest association being found in the area with the most pronounced iodine deficiency. This may have implications for future goiter prevalences in Third World countries, with their increasing use of tobacco. Half of goiter cases in this population could be ascribed to smoking.

Bone mineral content and bone metabolism during physiological GH treatment in GH-deficient adults--an 18-month randomised, placebo-controlled, double blinded trial

OBJECTIVE

To evaluate the effect of physiological adult growth hormone (GH) replacement on bones.

DESIGN

Thirty-six prospective severely growth hormone-deficient (GHD) adults (22 females and 14 males) were randomised to either 18 months of GH (0.03 mU/kg/day) or placebo treatment.

METHODS

Bone mineral density and content (BMD, BMC) and body composition were evaluated by dual energy X-ray absorptiometry at baseline and after 6, 12 and 18 months. Serum concentrations of insulin-like growth factor-I (IGF-I), IGF binding protein 3, osteocalcin, carboxyterminal propeptide of type I collagen, carboxyterminal crosslink telopeptide of type I collagen, amino-terminal propeptide of type III procollagen and urine pyridinolin and deoxypyridinolin were determined.

RESULTS

IGF-I levels increased from 63.2 microg/l (+/-10.1) to 193.6 (+/- 25.8) microg/l (mean (+/-s.e.)) (P<0.001 compared with placebo). Markers of bone turnover increased significantly from 142% to 227% of baseline values (all P<0.001 compared with placebo). Body composition changes were an increase of lean body mass and a decrease of fat mass resulting in a reduction of percentage body fat of +/- 1.8 (+/- 3.8) in the GH-treated group vs an increase of 1.0 (+/-2.9)) in the placebo-treated group (P=0.002).

CONCLUSIONS

No significant difference in BMD or BMC between the GH and placebo groups was found after 18 months. At several sites the variances of changes from baseline were significantly greater in the GH than in the placebo group, indicating an impact of the treatment. From baseline to 6 months an insignificant reduction of total BMD was seen while an increase of BMD was found from 6 to 18 months in the GH group compared with the placebo group. This placebo-controlled trial confirmed the longer term open studies on the effect on bones in patients with GHD, with an initial overrepresentation of bone resorption followed by an increase in BMD which at 18 months had reached baseline level.

Fracture risk is increased in patients with GH deficiency or untreated prolactinomas--a case-control study

OBJECTIVE

The pituitary secretes many hormones of significance to bone turnover and thus skeletal integrity. The aim of this study was to examine fracture risk in patients with pituitary disorders with special reference to GH deficiency and hyperprolactinaemia.

DESIGN

Case-control study.

MEASUREMENTS

Fracture occurrence.

PATIENTS

A self-administered questionnaire was issued to 537 consecutive patients with pituitary disorders excluding Cushing's disease. A total of 426 (79%) returned the questionnaire and 422 of these could be analysed. Each respondent was compared to three age- and gender-matched control respondents to the same questionnaire drawn randomly from the background population.

RESULTS

The patients had a mean age of 51.4 +/- 14.8 years. One hundred and eight patients had acromegaly, 86 had prolactinomas, 136 had non-functioning pituitary adenomas (NFPA), 23 had craniopharyngiomas, and 73 had other types of pituitary disorders. For the total group the fracture risk was not elevated either before or after confirmed diagnosis compared to controls. However, among the patients with prolactinomas, the fracture risk was significantly increased before (relative risk, RR = 1.6, 95% CI: 1.1--2.3) but not after diagnosis. In patients with NFPA, fracture risk was borderline significantly elevated following diagnosis (RR = 1.6, 95% CI: 1.0--2.6). Patients with subnormal stimulated peak GH values suggestive of GH deficiency had a significantly higher risk of fractures after diagnosis than patients who had normal stimulated peak GH values (odds ratio, OR = 4.90, 95% CI: 1.10--21.88).

CONCLUSIONS

Untreated prolactinomas were associated with a significant increase in fracture risk. Growth hormone deficiency was also associated with a higher fracture risk.

Dietary iodine intake and urinary iodine excretion in a Danish population: effect of geography, supplements and food choice

I deficiency diseases remain a health problem even in some developed countries. Therefore, measurement of I intake and knowledge about food choice related to I intake is important. We examined I intake in 4649 randomly selected participants from two cities in Denmark (Copenhagen and Aalborg) with an expected difference in I intake. I intake was assessed both by a food frequency questionnaire and by measuring I in casual urine samples. I excretion was expressed as a concentration and as estimated 24-h l excretion. Further, subgroups with low I intake were recognized. I intake was lower in Aalborg than in Copenhagen for all expressions, and lower than recommended in both cities if I intake from supplements was not included. Milk was the most important I source, accounting for about 44% of the I intake, and milk (P<0.001) and fish (P=0.009) intake was related to I excretion in a multiple linear regression model. Thus, risk groups for low I intake were individuals with a low milk intake, those with a low intake of fish and milk, those not taking I supplements and those living in Aalborg where the I content in drinking water is lower. Even individuals who followed the advice regarding intake of 200-300 g fish/week and 0.5 litres milk/d had an intake below the recommended level if living in Aalborg.

Parity is associated with increased thyroid volume solely among smokers in an area with moderate to mild iodine deficiency

OBJECTIVE

Pregnancy has been suggested as part of the explanation of the gender difference in the prevalence of goitre, but opposing results have been reported on the association between pregnancy and goitre. We investigated the association between parity and thyroid volume and a possible impact of iodine deficiency and tobacco smoking on this association.

DESIGN

A comparative, cross-sectional study of 3712 women randomly sampled from the general population in two geographical areas with moderate and mild iodine deficiency.

METHODS

The participants answered questionnaires with an obstetric anamnesis, and ultrasonography of the thyroid was performed. Data were analysed in linear models and logistic regression analysis to adjust for age, iodine status, use of oral contraceptives and smoking habits. Women with present or recent pregnancies were excluded from the analyses.

RESULTS

A higher thyroid volume was found among parous than among nulliparous women (P=0.007). The association between parity and thyroid volume was strongest in the youngest age groups, in the region with the most severe iodine deficiency, and among smokers. No association was found between parity and the prevalence of solitary or multiple thyroid nodules. Number of births, age at menarche or menopause, the number of fertile years, and age at first childbirth were not associated with thyroid volume.

CONCLUSION

Pregnancy increases thyroid volume, particularly when combined with tobacco smoking and iodine deficiency. The effect is probably reversible seen over a spectrum of several years.

Efficacy of the new long-acting formulation of lanreotide (lanreotide Autogel) in the management of acromegaly

Lanreotide Autogel is a new long-acting aqueous preparation of lanreotide for the treatment of acromegaly and is administered by deep sc injection from a small volume, prefilled syringe. The aim of this study was to evaluate the efficacy and safety of this new long-acting formulation in a large population of acromegalic patients previously responsive to lanreotide 30 mg, im (sustained release microparticle formulation). Lanreotide Autogel was administered by deep sc injection every 28 d to 107 patients (54 males and 53 females; mean age, 54 +/- 1.2 yr). All patients had been treated with lanreotide (30 mg) for at least 3 months before study entry and had a mean GH level less than 10 ng/ml after at least 4 subsequent im injections every 14 d (48%), 10 d (32%), or 7 d (20%). Treatment was switched from lanreotide 30 mg injected every 14, 10, or 7 d to 60, 90, or 120 mg lanreotide Autogel, respectively, every 28 d. After three fixed dose injections of lanreotide Autogel, mean lanreotide levels were similar to those obtained at steady state with lanreotide 30 mg. During lanreotide Autogel treatment, the control of acromegalic symptoms was comparable with that previously achieved during lanreotide 30 mg treatment. After 3 injections of lanreotide Autogel, mean GH (2.87 +/- 0.22 ng/ml) and IGF-I (317 +/- 15 ng/ml) values were comparable with those recorded at the end of lanreotide 30 mg treatment (GH, 2.82 +/- 0.19 ng/ml; IGF-I, 323 +/- 16 ng/ml). GH levels below 2.5 ng/ml and age-/sex-normalized IGF-I were achieved in 33% and 39% of patients during lanreotide 30 mg and lanreotide Autogel treatment, respectively. Diarrhea, abdominal pain, and nausea were reported by 38%, 22%, and 18% of patients during lanreotide 30 mg treatment and by 29%, 17%, and 9% of patients, respectively, during lanreotide Autogel treatment. In conclusion, this clinical study shows that lanreotide Autogel is at least as efficacious and well tolerated as lanreotide 30 mg. This new long-acting lanreotide formulation, lanreotide Autogel, which is administered from a small volume, prefilled syringe by deep sc injection, is therefore likely to improve the acceptability of medical treatment for patients requiring long-term somatostatin analog therapy.

Smoking as a risk factor for Graves' disease, toxic nodular goiter, and autoimmune hypothyroidism

To study the association between smoking and thyroid disease (Graves' disease [E05.0], nodular toxic goiter [E05.2], and autoimmune hypothyroidism [E03.9]) in a low-iodine intake area a case-control study was undertaken. A self-administered questionnaire was issued to 864 consecutive patients with hyperthyroidism and 628 patients with autoimmune hypothyroidism treated at five university or regional endocrinologic clinics in Denmark between January 1, 1990 and December 31, 1998. Each respondent was compared to an age- (+/- 5 years) and gender-matched normal control person randomly drawn from the background population. A total of 621 patients with hyperthyroidism (72%) and 411 patients with autoimmune hypothyroidism (66%) responded. Of these, 617 (542 females) and 408 (364 females) could be analyzed, respectively. There was an increased risk of both Graves' disease (odds ratio [OR] = 2.5, 95% confidence interval [CI]: 1.8-3.5), toxic nodular goiter (OR = 1.7, 95% CI: 1.1-2.5), and autoimmune hypothyroidism (OR = 1.5, 95% CI: 1.1-2.1) with ever smoking compared to never smoking in women, but not in men. With the high proportion of ever-smokers among women (56%), the attributable risk of smoking in women was 45% in Graves' disease, 28% in toxic nodular goiter, and 23% in autoimmune hypothyroidism. Ever use of oral contraceptives was associated with a slightly lower risk of Graves' disease in women, but not of toxic nodular goiter or autoimmune hypothyroidism. In conclusion, smoking is a powerful risk factor for thyroid disease, especially in populations with a high smoking frequency. Oral contraceptive use is associated with a slightly lower frequency of Graves' disease.

Increased risk of osteoporotic fractures in patients with Cushing's syndrome

OBJECTIVE

To evaluate if fracture risk was increased in patients with Cushing's syndrome due to the increased endogenous cortisol production.

DESIGN

Cohort.

METHODS

A self-administered questionnaire was mailed to 125 patients with Cushing's syndrome diagnosed between 1985 and 1999 in Denmark. The response of each patient was compared with that of three age- and gender-matched control subjects randomly drawn among respondents to the same questionnaire from the background population.

RESULTS

One hundred and four patients (83%) responded. The median age of the patients was 48 years (range 19-85 years). Sixty-eight had pituitary disease, 28 had adrenal disease, four had had both pituitary and adrenal surgery while four had not undergone surgery at the time of the study. The median time from diagnosis to surgery was 0.2 (range 0-3) years. Eighty-six percent were cured following surgery. There was an increased fracture risk within the last 2 years prior to diagnosis (incidence rate ratio 6.0, 95% confidence intervals (CI): 2.1-17.2). More than 2 years prior to diagnosis and following diagnosis there was no difference in fracture risk between patients and controls. The patients had more low-energy fractures than the controls (relative risk 5.4, 95% CI: 1.4-20.1). There was no difference in fracture risk between patients with adrenal or pituitary disease.

CONCLUSIONS

Patients with Cushing's syndrome had an increased fracture risk in a narrow time interval before diagnosis, while no increase in fracture risk could be demonstrated after diagnosis and treatment.

TSH-receptor antibody measurement for differentiation of hyperthyroidism into Graves' disease and multinodular toxic goitre: a comparison of two competitive binding assays

OBJECTIVES

Graves' disease is characterized by stimulating autoantibodies to the TSH-receptor (TRAb). The aim of this study was to compare the performance of a new TRAb assay based on competitive binding to recombinant human TSH-receptors (H-TRAb) with an assay employing purified porcine TSH-receptors (P-TRAb). Furthermore, to evaluate the applicability of the H-TRAb assay to discriminate between patients with hyperthyroidism due to Graves' disease (GD) and multinodular toxic goitre (MNTG).

DESIGN AND MEASUREMENTS

H-TRAb and P-TRAb were measured in patients with newly diagnosed hyperthyroidism due to GD (n = 106) and MNTG (n = 94). For comparison, TRAb was measured in patients with primary autoimmune hypothyroidism, euthyroid subjects with an enlarged thyroid gland by ultrasound, and healthy controls (n = 100 for each group). Patients were consecutively included from a population survey.

RESULTS

If the cut-off values recommended by the manufacturer for TSH-receptor antibody positivity were used for evaluation, the sensitivity of the H-TRAb assay vs. the P-TRAb assay in diagnosing GD was: 95.3/67.9% (P < 0.001). Specificity was (H/P-TRAb): 99/99%. The sensitivity of P-TRAb was increased if the upper 97.5% limit of measurements in controls was used as cut-off (H-TRAb vs. P-TRAb: 95.3/80.2%, P < 0.001). Specificity (H/P-TRAb): 98/98%. The difference between assay performance may partly be due to a better technical performance of the H-TRAb assay with more reliable results in the low range of measurements. However, even in GD patients with clearly measurable TRAb, 25% had a P-TRAb < 50% of the value expected from the H-TRAb measurement. This suggests that a subgroup of patients produce TRAb with a higher affinity for the human than the porcine TSH receptor. A relatively high proportion of patients with MNTG were TRAb positive (H-TRAb/P-TRAb: 17/9%). Characteristics of H-TRAb positive and negative MNTG patients were compared. There was no difference between size of thyroid gland and number of nodules by ultrasonography. H-TRAb positive patients had significantly higher serum T4 and T3 and a greater number were TPO-Ab positive.

CONCLUSIONS

H-TRAb diagnosed Graves' disease with a high sensitivity and specificity than P-TRAb. The high occurrence of TRAb in multinodular toxic goitre might in part reflect an overlap between Graves' disease and multinodular toxic goitre in some patients.

Evaluation of a semi-quantitative food frequency questionnaire to estimate iodine intake

OBJECTIVE

To evaluate a food frequency questionnaire (FFQ) used to assess the dietary intake of iodine.

DESIGN

The iodine intake determined by the FFQ was compared with 4-day dietary records and with iodine excretion in 24 h urine samples in a subgroup of participants in a cross-sectional study of iodine intake and thyroid diseases in Denmark. Furthermore, the intake of fish determined from the FFQ was compared with the intake of fish from a simple record kept for 3 months.

SUBJECTS

Women aged 25-30 y and 60-65 y.

RESULTS

Median iodine intake was similar when determined from the FFQ and from dietary records and the correlation between these measures was 0.52 (P < 0.001). Iodine intake was higher than iodine excretion (P < 0.001). The cross-check questions in the FFQ (for example the question 'How often did you get any kind of fish?') underestimated the intake. In contrast, the intake of a specific fish tended to be overestimated by the FFQ when compared with the 3 month record of fish intake.

CONCLUSION

The FFQ can be used to classify subjects into low and high iodine intake groups, but the level of iodine tends to be overestimated.

Serum Tg--a sensitive marker of thyroid abnormalities and iodine deficiency in epidemiological studies

Serum Tg is widely used in the control of thyroid cancer but also in the diagnosis of certain other thyroid diseases. Serum Tg may be useful in the characterization of the iodine status of a population, but little is known about determinants of serum Tg levels. We examined a random selection of 4,649 subjects from 2 regions in Denmark with different iodine status. Thyroid volume and structure were determined with ultrasonography, and thyroid function tests and Tg analysis were performed. The factor with the closest association with serum Tg levels was thyroid volume at ultrasonography (P < 0.001). Also thyroid nodularity (P < 0.001) and iodine excretion (P < 0.001) had close associations to serum Tg, even after adjusting for the influence of the other parameters. Thyroid dysfunction had a less pronounced but still highly significant association with serum Tg (P < 0.001), but no relation was found to serum TSH in general. The association with age seemed to rely on differences in the prevalence of thyroid abnormalities, and men had lower Tg levels than women of the same age. There was a marked difference in serum Tg between the two regions with slightly different iodine excretion also after adjusting for the other factors. In conclusion, serum Tg reflects thyroid abnormalities and thyroid function and is a sensitive marker of iodine deficiency in a population.

Alcohol consumption is associated with reduced prevalence of goitre and solitary thyroid nodules

OBJECTIVE

Goitre prevalence is dependent on iodine intake and smoking habits, but further risk factors have only been examined briefly. We examined the association between alcohol consumption and the prevalence of thyroid enlargement and nodularity.

DESIGN

Cross-sectional population study with ultrasonography of the thyroid gland and assessment of alcohol intake and smoking habits from questionnaires.

SUBJECTS

Four thousand six-hundred and forty-nine men and women aged 18-65 years, randomly selected from the Danish Civil Registration System.

MEASUREMENTS

Thyroid volume and prevalence of thyroid enlargement, multiple nodules or a solitary nodule in the thyroid.

RESULTS

Abstainers and participants with a low alcohol consumption (< 7 drinks/week) had the same prevalence of thyroid enlargement and nodularity, but participants with moderate (8-28 drinks/week for women, 8-42 for men) or high (> 28/42 drinks/week) alcohol consumption had much lower prevalence of thyroid abnormalities. Possible confounding by sex, age, iodine status and smoking was considered in all models. Odds ratios compared to abstainers for thyroid enlargement were 0.74 [95% confidence interval (CI) 0.57-0.96] for moderate- and 0.44 (95% CI 0.22-0.88) for high alcohol consumption. Odds ratios compared to abstainers for a solitary nodule were 0.64 (95% CI 0.42-0.96) for moderate- and 0.41 (95% CI 0.12-1.37) for high alcohol consumption. Mean thyroid volume was 13.5 ml among abstainers compared to 10.9 ml among participants with high alcohol consumption (P < 0.001). Both wine- and beer consumption were associated to lower prevalence of thyroid abnormalities.

CONCLUSIONS

Increasing levels of alcohol consumption were associated to lower prevalence of thyroid enlargement and to lower prevalence of a solitary nodule in the thyroid, and indications of a causal relationship were found.

Variations in urinary iodine excretion and thyroid function. A 1-year study in healthy men

OBJECTIVE

The iodine intake level in a population is determined in cross-sectional studies. A fraction of samples with iodine content below a certain level, e.g. 25 microg/l, may suggest iodine deficiency in part of the population. However, urinary iodine varies considerably from day to day and the fraction of low samples caused by dispersion remains unsettled.

DESIGN

A longitudinal study of 16 healthy men living in an area of mild to moderate iodine deficiency.

METHODS

We measured urinary iodine and creatinine concentrations, and serum TSH, total thyroxine (T4), free T4 index and total tri-iodothyronine (T3) in samples collected monthly for 1 year.

RESULTS

Average urinary iodine excretion was 57.0 microg/l (49.1 microg/24 h (corrected for creatinine excretion)) and varied from 29 to 81 microg/l (28 to 81 microg/24 h) between participants. Individual samples varied between 10 and 260 microg/l, and the variation around the mean was 2.4 times larger when calculated for the 180 individual samples compared with the 15 average annual values (1.7 times larger for estimated 24 h iodine excretion values). The fraction of individual samples below 25 microg/l was 6.7% (7.2% < 25 microg/24 h), whereas none of the participants had average iodine excretion below 25 microg/l or 25 microg/24 h. Participants with average annual iodine excretion below 50 microg/24 h had a negative correlation between iodine excretion and TSH, whereas a positive correlation was observed when average annual iodine excretion was above this level.

CONCLUSIONS

Seven per cent of individual urine samples indicated severe iodine deficiency without this being present in the group studied. Dispersion was reduced by 24% when using estimated 24 h urinary iodine excretion rather than urinary iodine concentration. Participants with moderate iodine deficiency (average annual urinary iodine excretion 25-50 microg/24 h) showed clear signs of substrate deficiency for thyroid hormone synthesis while participants with mild iodine deficiency (50-100 microg/24 h) did not.

Environmental iodine intake affects the type of nonmalignant thyroid disease

The relationship between the iodine intake level of a population and the occurrence of thyroid diseases is U-shaped with an increase in risk from both low and high iodine intakes. Developmental brain disorders and endemic goiter caused by severe iodine deficiency may seriously deteriorate overall health status and economic performance of a population. Severe iodine deficiency with a median 24-hour urinary iodine excretion of the population below 25 microg needs immediate attention and correction. Less severe iodine deficiency with median urinary iodine excretion below 120 microg per 24 hours is associated with multinodular autonomous growth and function of the thyroid gland leading to goiter and hyperthyroidism in middle aged and elderly subjects. The lower the iodine intake, the earlier and more prominent are the abnormalities. At the other end of the spectrum, severely excessive iodine intake starting at median urinary iodine excretion levels around 800 microg per 24 hours is associated with a higher prevalence of thyroid hypofunction and goiter in children. A number of studies indicate that moderate and mild iodine excess (median urinary iodine >220 microg per 24 hours) are associated with a more frequent occurrence of hypothyroidism, especially in elderly subjects. The exact mechanism leading to this has not been clarified, and more studies are needed to define the limits of excessive iodine intake precisely. Due to the frequent occurrence of thyroid disorders, proper monitoring and control of the population iodine intake level is a cost-effective alternative to diagnosing, therapy and control of the many individual cases of thyroid diseases that might have been prevented.

Incidence and late prognosis of cushing's syndrome: a population-based study

The main purpose was to assess the incidence and late outcome of Cushing's syndrome, particularly in Cushing's disease. Information for all patients diagnosed with Cushing's syndrome during an 11-yr period in Denmark was retrieved. The incidence was 1.2-1.7/million.yr (Cushing's disease), 0.6/million.yr (adrenal adenoma) and 0.2/million.yr (adrenal carcinoma). Other types of Cushing's syndrome were rare. In 139 patients with nonmalignant disease, 11.1% had died during follow-up (median, 8.1 yr; range, 3.1-14.0), yielding a standard mortality ratio (SMR) of 3.68 [95% confidence interval (CI), 2.34-5.33]. The SMR was partly attributable to an increased mortality within the first year after diagnosis. Eight patients died before treatment could be undertaken. The prognosis in patients with malignant disease was very poor. Patients in whom more than 5 yr had elapsed since initial surgery were studied separately, including a questionnaire on their perceived quality of health. In 45 patients with Cushing's disease who had been cured through transsphenoidal neurosurgery, only 1 had died (SMR, 0.31; CI, 0.01-1.72) compared with 6 of 20 patients with persistent hypercortisolism after initial neurosurgery (SMR, 5.06; CI, 1.86-11.0). In patients with adrenal adenoma, SMR was 3.95 (CI, 0.81-11.5). The perceived quality of health was significantly impaired only in patients with Cushing's disease and appeared independent of disease control or presence of hypopituitarism. It is concluded that 1) Cushing's syndrome is rare and is associated with increased mortality, in patients with no concurrent malignancy also; 2) the excess mortality was mainly observed during the first year of disease; and 3) the impaired quality of health in long-term survivors of Cushing's disease is not fully explained.

Folate intake, lifestyle factors, and homocysteine concentrations in younger and older women

BACKGROUND

An elevated total homocysteine (tHcy) concentration is considered to be an independent risk factor for cardiovascular diseases and has also been associated with an increased risk of neural tube defects.

OBJECTIVE

The objective of this study was to investigate folate intake, folate status, and the association between folate intake, other dietary and lifestyle factors, and tHcy concentrations in young and older women.

DESIGN

tHcy concentrations were measured in 290 young women aged 25-30 y and in 288 older women aged 60-65 y. All participants completed questionnaires about factors including lifestyle, health, and use of vitamin supplements. Red blood cell folate was measured in 204 of the participants. A subgroup of 258 participants completed dietary records.

RESULTS

Median tHcy was 7.6 micromol/L (range: 6.5-8.9) in the younger women and 9.4 micromol/L (7.7-11.1) in the older women. Folate intake from diet was 283 (224-348) and 268 (210-326) microg/d, respectively, in the 2 age groups. Folic acid intake from supplements (P: < 0.001 for the younger women and P: = 0.026 for the older women) and total folate intake (P: = 0.024 and P: = 0.079) were inversely associated with log tHcy in multiple linear regression analyses. Smoking status, coffee consumption, systolic blood pressure, and body mass index were positively associated and estrogen replacement therapy and tea consumption were inversely associated with log tHcy in some of the models.

CONCLUSIONS

According to the criteria used, between 1% and 36% of the women had suboptimal folate intake. Folic acid is a strong predictor of tHcy concentration; however, several dietary and other lifestyle factors seem to be important as well.

Thyroid disorders in mild iodine deficiency

Comparative epidemiologic studies in areas with low and high iodine intake and controlled studies of iodine supplementation have demonstrated that the major consequence of mild-to-moderate iodine deficiency for the health of the population is an extraordinarily high occurrence of hyperthyroidism in elderly subjects, especially women, with risk of cardiac arrhythmias, osteoporosis, and muscle wasting. The hyperthyroidism is caused by autonomous nodular growth and function of the thyroid gland and it is accompanied by a high frequency of goiter. Pregnant women and small children are not immediately endangered but the consequences of severe iodine deficiency for brain development are grave and a considerable safety margin is advisable. Moreover, a shift toward less malignant types of thyroid cancer and a lower radiation dose to the thyroid in case of nuclear fallout support that mild-to-moderate iodine deficiency should be corrected. However, there is evidence that a high iodine intake may be associated with more autoimmune hypothyroidism, and that Graves' disease may manifest at a younger age and be more difficult to treat. Hence, the iodine intake should be brought to a level at which iodine deficiency disorders are avoided but not higher. Iodine supplementation programs should aim at relatively uniform iodine intake, avoiding deficient or excessive iodine intake in subpopulations. To adopt such a strategy, surveillance programs are needed.

Comparative study of thyroid function and types of thyroid dysfunction in two areas in Denmark with slightly different iodine status

OBJECTIVE

The pattern of thyroid dysfunction seems to depend on the iodine status of the population. Prevalence of thyroid dysfunction could be a parameter to consider when evaluating iodine deficiency disorders in a population.

DESIGN

Comparative cross-sectional investigation in two regions in Denmark with marginally different iodine excretion.

METHODS

A random selection of 4649 participants from the Civil Registration System in Denmark in age groups between 18 and 65 years were examined. Thyroid dysfunction was evaluated from blood samples and questionnaires, and compared with results from ultrasonography.

RESULTS

Median iodine excretion was 53 microg/l in Aalborg and 68 microg/l in Copenhagen. Previously diagnosed thyroid dysfunction was found with the same prevalence in the regions. Serum TSH was lower in Aalborg than in Copenhagen (P=0. 003) and declined with age in Aalborg, but not in Copenhagen. Not previously diagnosed hyperthyroidism was found with the same overall prevalence in the regions, but in age >40 years hyperthyroidism was more prevalent in Aalborg (1.3 vs 0.5%, P=0.017). Not previously diagnosed hypothyroidism was found more frequently in Aalborg (0.6 vs 0.2%, P=0.03). Hyperthyroidism was more often associated with macronodular thyroid structure at ultrasound in Aalborg and hypothyroidism was more often associated with patchy thyroid structure in Copenhagen.

CONCLUSIONS

Significant differences in thyroid dysfunction were found between the regions with a minor difference in iodine excretion. The findings are in agreement with a higher prevalence of thyroid autonomy among the elderly in the most iodine-deficient region.

Goitre prevalence and thyroid abnormalities at ultrasonography: a comparative epidemiological study in two regions with slightly different iodine status

OBJECTIVE

The association between severe iodine deficiency and endemic goitre is well established, but little information is available on the relation between milder degrees of iodine deficiency and goitre prevalence.

SUBJECTS

In a comparative epidemiological study performed in two regions in Denmark, we examined 4649 subjects from the general population, women aged 18-65 years and men aged 60-65 years.

METHODS

Ultrasonography and palpation of the thyroid was performed in all participants. Iodine excretion was measured in casual urine samples. Previous thyroid disease was detected by questionnaires, personal interviews and tracing of records.

RESULTS

The median iodine excretion was 61 microg/l (mild iodine deficiency (ID)) and 45 microg/l (moderate ID) in the two regions. Median thyroid volume at ultrasonography was 11. 9 ml (mild ID) and 13.6 ml (moderate ID), P <0.001, and thyroid enlargement was found in 15.0% (mild ID) and 22.6% (moderate ID), P<0.001. Goitre prevalence increased in both regions with age to the age group 40-45 years, but not after that age. Subjects who had moved from the moderate ID to the mild ID area had the same prevalence of thyroid enlargement as the subjects staying permanently in the mild ID area. Thyroid nodules at ultrasonography were found in 30% in both regions, but nodules were larger and more often palpable in the moderate ID area. Palpable goitre was found in 9.8% (mild ID) and 14.6% (moderate ID), P<0.001. The greatest regional difference in thyroid abnormalities was found among men.

CONCLUSION

Marked differences in the prevalence of thyroid abnormalities were found in these regions with modest differences in iodine excretion.

Postpartum thyroid dysfunction in pregnant thyroid peroxidase antibody-positive women living in an area with mild to moderate iodine deficiency: is iodine supplementation safe?

In moderately iodine-deficient, pregnant, thyroid peroxidase antibody (TPO-Ab)-positive women the role of iodine supplementation in the development of postpartum thyroid dysfunction (PPTD) was studied in a placebo-controlled, randomized, double blind trial. Screening for TPO-Ab was performed in early pregnancy in a population of healthy pregnant Danish women with no previous diagnosed thyroid disease (prevalence, 117 of 1,284; 9.1%). The participants were randomized, stratified according to TPO-Ab level, to three groups. All participants received a daily vitamin and mineral tablet with 150 microg iodine or no iodine. The +/+ group received iodine during pregnancy and the postpartum period, the +/- group received iodine during pregnancy only, and the -/- group received no iodine supplementation. A total of 66 TPO-Ab positive women were followed, and in the postpartum period sera were collected at 8-week interval for biochemical evaluation of thyroid function and antibody level. Compliance was evaluated by 24-h urinary iodine measurements. PPTD developed in 55% of the participants. In 67% of the cases abnormal TSH was accompanied by abnormalities in thyroid hormones, whereas 33% had abnormal serum TSH only. There was no statistically significant difference in the frequency of PPTD in the three groups: +/+ group, 59% (95% confidence interval, 36-79%); +/- group, 60% (36-81%); and -/- group, 46% (26-67%). There were also no differences in the severity of the PPTD, as evaluated by duration and grade of deviation of TSH and thyroid hormones from normality. The occurrence, severity, and type of PPTD predominantly depended on the TPO-Ab level: TPO-Ab below 200 U/L at screening, 35% developed PPTD; TPO-Ab of 200-900 U/L, 54%; and TPO-Ab above 900 U/L, 75% developed PPTD. Women with low levels of antibodies predominantly remained euthyroid or had hyperthyroidism only, whereas women with high antibody levels had hyperthyroidism followed by hypothyroidism or hypothyroidism only. We conclude that iodine supplementation (150 microg) during pregnancy and the postpartum period to TPO-Ab-positive women living in an area with mild to moderate iodine deficiency did not induce or worsen PPTD. The study confirmed that screening for TPO-Ab in early pregnancy can predict women at high risk for development of PPTD.

Diagnosis of growth hormone (GH) deficiency in adults with hypothalamic-pituitary disorders: comparison of test results using pyridostigmine plus GH-releasing hormone (GHRH), clonidine plus GHRH, and insulin-induced hypoglycemia as GH secretagogues

The insulin tolerance test (ITT) is widely accepted as the method of choice to evaluate GH secretion capacity in adults with hypothalamic-pituitary disorders. However, the test is not suitable in the elderly or in patients with cardiovascular disease or seizure disorders. In recent years alternatives to the ITT have been introduced. The purpose of the present study was to investigate the diagnostic outcome with the ITT, the pyridostigmine plus GHRH (PD + GHRH) test, the clonidine plus GHRH (CLO+GHRH) test, and insulin-like growth factor I (IGF-I) in an unselected group of patients with hypothalamic-pituitary disease. An evaluation of the reproducibility of the different stimulation tests was included in the study. Based on repeated testing with the various GH stimulation tests in healthy adult males and females, the lower limits of normality for the ITT, the PD+GHRH test, and the CLO+GHRH test were 3.92, 12.8, and 19.0, microg/L, respectively. A consecutive group of 26 unselected patients with hypothalamic-pituitary disorders, 13 males and 13 females (median age, 44 ys), were tested twice with all stimulation tests, except that only 10 patients were tested once with the CLO+GHRH test due to side-effects related to clonidine. The peak GH responses between test 1 and test 2 correlated significantly in both the ITT and the PD + GHRH test (P < 0.02), and no significant difference was observed in the median peak response to repeated testing. In addition, no sex difference was observed. The coefficients of variation (CV) were 96% (ITT) and 45% (PD + GHRH), but in the majority of patients low values were repeatedly low. The peak GH response was significantly higher during the PD+GHRH test than during the ITT (P = 0.008). In the 10 patients tested with the PD+GHRH and CLO+GHRH tests there was no significant difference in the peak GH response (P = 0.398). When the test specific cut-off values were used, no significant difference in diagnostic outcome was observed between the various tests (P > 0.3). In contrast, the diagnosis obtained with IGF-I differed significantly from all GH stimulation tests (P < 0.03). Twenty (77%) and 22 (85%) patients were diagnosed to be GH deficient with the ITT and the PD+GHRH test, respectively. Of the 14 patients with multiple pituitary failure (>2 hormones affected), GH deficiency was present in more than 90% regardless of the type of stimulation test used. The IGF-I levels were only subnormal in 42% of the patients and did not correlate with the peak GH responses in any of the stimulation tests (P > 0.05). Except for 1 patient all patients with subnormal IGF-I were GH deficient in all stimulation tests. It is concluded that in patients with hypothalamic-pituitary disease and a normal IGF-I level 2 stimulation tests should be performed to establish a diagnosis of GH deficiency. In patients with a subnormal IGF-I value a single GH stimulation test should be sufficient to confirm the presence of GH deficiency.

Fractures in patients with primary idiopathic hypothyroidism

AIM

To study fracture risk and risk factors for fractures in patients with primary idiopathic hypothyroidism (ICD 10: E03.9).

DESIGN

Historical follow-up.

MATERIAL AND METHODS

A self-administered questionnaire was issued to 628 patients with primary idiopathic levothyroxine-substituted hypothyroidism. A total of 412 (65.6%) responded and of these, 408 could be analyzed. The 408 respondents were age- (+/- 5 years) and gender-matched with 408 normal controls randomly selected from the background population who responded to the same questionnaire.

RESULTS

Overall fracture risk was increased in patients compared to controls (relative risk: RR = 1.6, 95% CI: 1.0-2.5). However, the increase was temporary and limited to the period within the first 2 years after the diagnosis of hypothyroidism (RR = 3.1, 95% CI: 1.4-7.0). Before the diagnosis and more than 2 years after the diagnosis, the fracture risk in patients did not deviate from that of the controls. The increase in fracture risk was only significant in the age group above 50 years (RR = 1.8, 95% CI: 1-3.2), and was limited to the forearms (RR = 3.0, 95% CI: 1.4-6.3 for the entire patient population).

CONCLUSIONS

There was a temporary increase in fracture risk within the first 2 years after diagnosis of primary idiopathic hypothyroidism. The fracture risk was mainly increased in the age group above 50 years, and the increased risk was limited to the forearms.

Opposite variations in maternal and neonatal thyroid function induced by iodine supplementation during pregnancy

Whereas the consequences of extremes in iodine intake are well described, much less is known about the effect of more moderate variations in maternal iodine intake on fetal thyroid function. The present study performed in Denmark with mild to moderate iodine deficiency dealt with the effect of maternal iodine supplementation on thyroid function in the mother at term and in the fetus/neonate. Serum was collected consecutively from pregnant women at term (n = 144) and from cord blood (n = 139). Forty-nine women had a regular intake of vitamin and mineral tablets with iodine (150 microg/day) during pregnancy, and 95 took no artificial iodine supplementation. Iodine supplementation (+I) induced opposite variations in thyroid function in the mother and the fetus. In +I mothers, TSH was 7.6% lower than in mothers with no supplementation (P < 0.05). In cord blood, on the contrary, TSH was 27.3% higher in the +I group (P < 0.05). The variations were caused by opposite shifts in TSH frequency distribution in mothers and neonates. The association between iodine supplementation and high serum TSH in the neonates was further substantiated by an inverse correlation between thyroglobulin and TSH in cord blood (P < 0.001), whereas no specific pattern was observed in the mothers. High serum thyroglobulin was a marker of low iodine intake in both mothers and neonates. The results suggest that the fetal thyroid, at least in areas of mild iodine deficiency, is more sensitive to the inhibitory effect of iodine than hitherto anticipated.

Rapid MEN 2A gene carrier identification using primer-specific PCR amplification

DNA testing is of great importance in families with multiple endocrine neoplasia (MEN) type 2A to identify non-mutant carrying family members and asymptomatic mutation carriers, and also to confirm the diagnosis in patients who already show clinical or biochemical signs of disease. Several point mutations of the RET proto-oncogene on exons 10 and 11 are associated with the disease, which is characterized by medullary thyroid carcinoma, pheochromocytoma and hyperparathyroidism. The aim of the present study was to develop and evaluate a simple method, which indicates the mutational status of members of families where the site of the point mutation is known. The method is illustrated by the detection of mutation TGC-->TAC of codon 611, which is one of the well-known mutations associated with MEN 2A. The method involves the PCR technique with allele-specific primers and detection of the amplified sequences with biotinylated probes. There was a clear-cut difference between the readings from affected and unaffected subjects. The subjects had been evaluated independently and all subjects harboring the mutation also had clinical disease. The method provides a simple and reliable diagnostic tool for DNA screening of members of families with a known mutation of the RET-gene.

Validation of ultrasonography of the thyroid gland for epidemiological purposes

Ultrasonography of the thyroid is often used in epidemiological surveys, thus thorough characterization of the interobserver variation of the different parameters obtained is important. Various methods have been used for measuring thyroid volume, and different formulas have been used for calculation of thyroid volume from the measured dimensions. In this article, two principles of thyroid volume measurement are described in detail: the wellknown method based on the three axes of each lobe and a new principle based on planimetry in two planes. The interobserver variation of the examination and the measuring procedure in itself were tested on 25 participants in a population study. A comparison of postmortem ultrasonography of the thyroid and results of an autopsy was performed. Good correlation and agreement between observers was found for thyroid volume (r = 0.98) and prevalence of thyroid nodules (kappa = 0.72), whereas echogenecity and echopattern showed little agreement. The correlation of thyroid volume by ultrasonography to autopsy results was satisfactory (r = 0.93), but the volume tended to be slightly underestimated even when using the formula pi/6(= 0.52)*length*width*depth. No major differences were found between the performance of the two principles of volume calculation. We conclude that when the measuring procedure is well defined, results of ultrasonography are comparable between observers for thyroid volume and prevalence of thyroid nodules, but not for echogenecity or echopattern. The formula of length*depth*width*pi/6 is suitable for thyroid volume measurement.

Graves' disease in the Inuit population of Greenland. Presentation of five cases observed during a two month period

Thyroid hormones are important for metabolic regulation. A number of studies have dealt with the effect of arctic living on thyroid hormone secretion and metabolism in healthy animals and humans. Little is however known of the effect of arctic living on the occurrence of thyroid diseases. In a study from Upernavik, Greenland no cases of hyperthyroidism were observed over the 25 years period from 1950 to 1974. We present five cases of hyperthyroidism due to Graves' disease observed during a two month period in Nuuk Greenland. The discrepancy could be due to improved diagnostic methods and activity or to a real increase in incidence. Systematic studies of thyroid disorders in Greenland are warranted.

Iodine in drinking water varies by more than 100-fold in Denmark. Importance for iodine content of infant formulas

The iodine intake level of the population is of major importance for the occurrence of thyroid disorders in an area. The aim of the present study was to evaluate the importance of drinking water iodine content for the known regional differences in iodine intake in Denmark and for the iodine content of infant formulas. Iodine in tap water obtained from 55 different locations in Denmark varied from <1.0 to 139 microg/l. In general the iodine content was low in Jutland (median 4.1 microg/l) with higher values on Sealand (23 microg/l) and other islands. Preparation of coffee or tea did not reduce the iodine content of tap water with a high initial iodine concentration. A statistically significant correlation was found between tap water iodine content today and the urinary iodine excretion measured in 41 towns in 1967 (r=0.68, P<0.001). The correlation corresponded to a basic urinary iodine excretion in Denmark of 43 microg/24h excluding iodine in water and a daily water intake of 1.7 l. The iodine content of infant formulas prepared by addition of demineralized water varied from 37 to 138 microg/l (median 57 microg/l, n=18). Hence the final iodine content would depend heavily on the source of water used for preparation. We found that iodine in tap water was a major determinant of regional differences in iodine intake in Denmark. Changes in water supply and possibly water purification methods may influence the population iodine intake level and the occurrence of thyroid disorders.

Differences in reproducibility and peak growth hormone responses to repeated testing with various stimulators in healthy adults

In healthy adults, GH responses to provocative testing are variable between subjects. Information on the intra-subject variability is limited, despite the importance attached to GH stimulation tests in the diagnosis of GH deficiency. We have investigated and compared the variability of different GH stimulation tests in a group of healthy control subjects. In 16 healthy non-obese adults, two insulin tolerance tests (ITT) (0.15 IU/kg body weight i.v. and a fall in blood glucose < or = 2.2 mmol/l) two GHRH tests (1 microgram/kg body weight i.v.), and two clonidine (CLO) (300 micrograms p.o.) + GHRH (60 min later) tests were performed in the morning after an overnight fast. A pyridostigmine (PD) (120 mg p.o. 60 min before GHRH) + GHRH test was performed twice in an extended group of 31 healthy adult subjects. A wide range of GH responses was observed. Both during the ITT and the GHRH test, low values in the range generally recognized to reflect impairment of GH secretory status were encountered. The median (range) peak GH responses in tests 1 and 2 were: (a) ITT: 14.4 micrograms/l (4.1-71.1) and 14.0 micrograms/l (0.09-69.5), (b) GHRH test: 21.7 micrograms/l (0.71-56.2) and 18.4 micrograms/l (1.6-55.1); (c) CLO + GHRH test: 57.4 micrograms/l (22.9-209) and 65.8 micrograms/l (12.2-206); (d) PD + GHRH test: 36.5 micrograms/l (9.1-125) and 44.6 micrograms/l (6.3-101). The coefficients of variation (CV) were: 58% (ITT), 45% (GHRH), 46% (CLO + GHRH) and 26% (PD + GHRH). The peak GH responses were significantly different in all tests (CLO + GHRH > PD + GHRH > GHRH > ITT). In the individual subject, there was no systematic correlation between the peak GH responses in the different stimulation tests. In conclusion, we found that the stimulated GH responses were highly variable in all tests, and that the peak GH responses differed. Test results in patients should be evaluated against test-specific reference values, and caution is justified in the interpretation of low responses in a single test.

Low incidence rate of overt hypothyroidism compared with hyperthyroidism in an area with moderately low iodine intake

In areas with relatively high iodine intake, the incidence rate of hypothyroidism is several-fold higher than that of hyperthyroidism. Recently, we found a similarly high prevalence rate of subclinical hypothyroidism compared with hyperthyroidism in a high iodine intake area, while a relatively low prevalence of subclinical hypothyroidism was observed in a low iodine intake area. In the present study we compared the incidence rate (newly diagnosed in primary care and at hospital) of overt hypothyroidism with that of hyperthyroidism in a well-defined geographical area in Jutland, Denmark, with an iodine intake around 60 microg/day. The number of personsxyears studied was 569,108. Data on hyperthyroidism have been published previously. The overall incidence of hypothyroidism was 13.5/100,000 per year (F/M 22.9/3.6), hyperthyroidism 38.7/100.000 per year (F/M 63.0/13.0). The incidence of hypothyroidism was steadily increasing with age up to 80/100,000 per year in subjects older than 70 years of age, but apart from congenital hypothyroidism it was lower than that of hyperthyroidism at all ages. The majority of patients (79%) was diagnosed to have spontaneous autoimmune hypothyroidism (16% with goiter, 84% with no thyroid visible or palpable). In conclusion, in an area with moderately low iodine intake, hypothyroidism was considerably less common than hyperthyroidism. This is in contrast to findings in high iodine intake areas. The iodine intake of an area seems to be of major importance for the pattern of thyroid disorders observed.

Iodine intake and the pattern of thyroid disorders: a comparative epidemiological study of thyroid abnormalities in the elderly in Iceland and in Jutland, Denmark

Thyroid abnormalities are common in all populations, but it is difficult to compare results of epidemiological studies, because different methods have been used for evaluation. We studied the importance of the population iodine intake level for the prevalence rate of various thyroid abnormalities in elderly subjects. Random samples of elderly subjects (68 yr) were selected from the central person registers in Jutland, Denmark, with low (n = 423) and, in Iceland, with longstanding relatively high (n = 100) iodine intake. Females from Jutland had a high prevalence of goiter or previous goiter surgery (12.2%), compared with males from Jutland (3.2%) and females (1.9%) and males (2.2%) from Iceland. Abnormal thyroid function was very common in both areas, with serum TSH outside the reference range in 13.5% of subjects from Jutland and 19% of those from Iceland. In Jutland, it was mainly thyroid hyperfunction (9.7% had low, 3.8% had high serum TSH), whereas in Iceland, it was impaired thyroid function (1% had low, 18% had high serum TSH). All subjects with serum TSH more than 10 mU/L had autoantibodies in serum, but antibodies were, in general, more common in Jutland than in Iceland. Thus, thyroid abnormalities in populations with low iodine intake and those with high iodine intake develop in opposite directions: goiter and thyroid hyperfunction when iodine intake is relatively low, and impaired thyroid function when iodine intake is relatively high. Probably, mild iodine deficiency partly protects against autoimmune thyroid disease. Thyroid autoantibodies may be markers of an autoimmune process in the thyroid or secondary to the development of goiter.

[Iodine intake in Denmark]

Iodine deficiency with a high frequency of goitre and, in severely affected areas, cretinism is common in some areas of the world. In Denmark the iodine intake as evaluated by urinary iodine excretion has been at a stable low level for many years, except for the part of the population now taking iodine supplementation as part of vitamin/ mineral preparations. The iodine intake is lowest in the western part of the country where an epidemiological study of elderly subjects has demonstrated a high frequency of goitre and hyperthyroidism in women. This supports the suggestion of a controlled moderate increase in iodine intake via an iodine supplementation program.

Reproducibility of growth hormone and cortisol responses to the insulin tolerance test and the short ACTH test in normal adults

Previous studies have demonstrated poor reproducibility of growth hormone (GH) responses to insulin tolerance testing (ITT). In order to investigate whether this is a particular feature of GH secretion we studied the reproducibility of the GH and cortisol responses to ITT simultaneously and also compared the latter with the reproducibility during short ACTH testing (SAT). Eight normal men (age 26-50) and 8 normal women (age 27-45) underwent 2 ITT and 2 SAT. In the ITT no systematic differences were observed between test 1 and 2 concerning blood glucose, GH and cortisol before and after stimulation. Similar results were obtained for cortisol during SAT. During ITT reproducibility was good for the cortisol response (coefficient of variation [CV] 10%, no sex differences) but poor for the GH response (CV 41% in men, 104% in women). Reproducibility was good for the cortisol response in SAT (CV 12%, no sex differences). The peak cortisol values during ITT (mean 585, range 448-775 nmol/l) were significantly lower than in the 2 SAT (mean 723, range 486-918 nmol/l). We conclude that the GH response during testing is more variable than the cortisol response. This could account for some of the difficulties encountered in the diagnosis of GH deficiency in adults.

Iodine. Do we need an enrichment program in Denmark?

A working group was established to evaluate the need for iodine enrichment in Denmark. Judged from studies of urinary iodine excretion and one dietary survey the intake of iodine in Denmark is low compared with recommended intakes. The occurrence of non-toxic goitre is relatively high; between 9 and 13% in elderly women. Furthermore, a high occurrence of toxic goitre has been seen in the western part of Denmark. On the other hand, an increased or a high intake of iodine may lead to hyperthyroidism and thyroiditis. The working group concluded that an increase in iodine intake in the Danish population is needed and the best way to achieve this is to iodize all salt. To avoid side effects of a sudden large increase in iodine intake the initial amount of iodine in salt will only be 2 ppm.

Test of growth hormone secretion in adults: poor reproducibility of the insulin tolerance test

The insulin tolerance test (ITT) is regarded as the most reliable provocative test in the diagnosis of growth hormone (GH) deficiency in adults. In the present study the test was evaluated by investigating the range of GH responses in normal adult males and females and the intra-individual reproducibility of the test. Sixteen healthy non-obese adults, eight males (median age 31.5 years) and eight females (median age 31.8 years) were tested twice with the ITT, with a minimum of 72 h between each test. The females were tested between day 3 and day 10 of their menstrual cycles. Adequate hypoglycemia was achieved in all cases with a median nadir blood glucose of 1.3 mmol/l (range 0.8-2.0). Growth hormone in serum was measured by immunoradiometric assay and low values were confirmed by a different assay. Median peak GH concentration responses to the ITT were: in males 27.9 micrograms/l, range 5.0-71.1 (test 1) and 30.5 micrograms/l, range 7.9-69.5 (test 2); and in females 9.0 micrograms/l, range 4.1-17.9 (test 1) and 8.4 micrograms/l, range 0.09-42.4 (test 2). The rise in GH concentration during the ITT was higher in males than in females. In the males, all stimulated GH values were > or = 5.0 micrograms/l. In the females, four out of 16 tests gave values below 5.0 micrograms/l and in one test the GH value was around the detection limit of the assays. There was poor reproducibility during repeated testing, with no correlation between the results of the two tests. The results did not correlate to the magnitude of the hypoglycemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary iodine excretion and individual iodine supplementation among elderly subjects: a cross-sectional investigation in the commune of Randers, Denmark

Several studies have demonstrated that the iodine intake is relatively low in Denmark. However, the results are difficult to interpret because no information has been given on the frequency of individual iodine supplementation. We performed a cross-sectional study of elderly subjects living in the commune of Randers, Denmark. Urinary iodine excretion was measured in the 423 participants (185 males, 238 females) and a careful history was taken on any possible intake of supplementary iodine. The median urinary iodine excretion was 48.3 micrograms/g creatinine for the whole population (40.8 micrograms/g creatinine in males, 53.2 micrograms/g creatinine in females). In the part of the population that did not take iodine supplementation (46.7%) the median value was 36.1 micrograms/g creatinine (males 33.8; females 38.8). Regular iodine supplementation taken as an iodine-containing vitamin/mineral tablet was found in 30.8% of the population. This increased the urinary iodine excretion to a median level of 80.5 micrograms/g creatinine (males 62.0; females 88.0). The study shows that the basic iodine intake level is overestimated if individual iodine supplementation is not taken into account. Such supplementation may lead to median iodine excretion values that seem reasonable, even if the iodine intake of the part of the population not taking iodine (in this study, nearly half of the population) is low.

Growth hormone and thyroid function: is secondary thyroid failure underdiagnosed in growth hormone deficient patients?

Thyroid hormones and the GH/IGF-1 system show considerable mutual interference which may have physiological, pathophysiological and clinical importance. GH therapy of children and adults may induce a fall in serum T4, which seems to be due to an effect on the deiodination of T4 to T3. Animal studies suggest that the alterations in thyroid hormones in tissue may be much more prominent than the changes observed in serum. It is possible that the GH deficiency seen in the majority of patients with pituitary/hypothalamic disorders may mask secondary hypothyroidism in some patients by giving a relatively high serum T4. GH therapy may then unmask the hypothyroidism. In accordance with such a mechanism GH deficient children evaluated thoroughly to exclude secondary thyroid failure before GH administration do not develop thyroid insufficiency during GH substitution therapy. It is suggested that thyroid insufficiency should be considered in GH deficient patients with low normal serum T4.

Impaired growth hormone secretion in patients operated for pituitary adenomas

The frequency of growth hormone (GH) deficiency in patients operated for pituitary neoplasms of various size and type was investigated using the insulin tolerance test. 45 patients were included in the study. 20 of the patients had a non-hormone secreting pituitary neoplasm, 9 had GH-, 6 ACTH-, 7 prolactin secreting adenomas and 3 had a craniopharyngeoma. Complete endocrinological examination was obtained in all patients after pituitary surgery. Apart from patients operated for GH secreting adenomas, GH deficiency was very common after pituitary surgery (92%), even in patients operated for small lesions. Among the 45 patients LH/FSH deficiency was found in 33%, ACTH in 33%, TSH in 18% and ADH deficiency in 9% of the patients. In this study, impaired GH secretion was found to be independent of the size of the tumors and was present in nearly all patients after pituitary surgery (with exception of GH secreting adenomas). Deficiencies of other pituitary hormones were predominantly observed after surgery for large tumors.

Iodine status in neonates in Denmark: regional variations and dependency on maternal iodine supplementation

Iodine status of 147 neonates born in five different regions of Denmark was evaluated in relation to the iodine content of breast milk and iodine supplementation taken by the mother. Approximately two-thirds of the women had not received iodine supplementation. They had low iodine concentrations in breast milk and urinary iodine concentrations of the neonates at day 5 were low. The median values (milk/urine) were 33.6/31.7 micrograms/l (Randers 22/26, Ringkøbing 29/16, Aalborg 36/31. Arhus 54/41 and Copenhagen 55/59 micrograms/l). Higher values were found in the group where tablets containing iodine had been taken (milk/urine: 57.0/61.0 micrograms/l). In general, the values are low compared with internationally recommended levels. We suggest that mothers without autoimmune thyroid disease should receive iodine supplementation in the form of vitamin/mineral tablets containing iodine (150 micrograms per tablet).

[Clinical significance of changing from a second to a third generation thyroid stimulating hormone (TSH) assay]

In recent years new sensitive immunochemoluminiscentic methods to measure thyroid stimulating hormone, TSH have been introduced. In this investigation we have made a comparison between an older, less sensitive, second generation TSH assay and a new, sensitive, third generation TSH assay in order to evaluate if new information of clinical value is obtained. We found that 20% of all the sera that were sent to the laboratory for TSH measurement showed low values. In the sera with low TSH concentration a great variation was observed between the "correct" values found with the third generation assay and the values found with the less sensitive second generation assay. We conclude, that since many sera sent to a routine laboratory have low TSH concentrations, and since it is of clinical importance to know the correct TSH value in many different patient categories, a third generation TSH assay is recommended in the daily routine.

Hypercalcaemic crisis after excessive topical use of a vitamin D derivative

Topical application of the vitamin D analogue calcipotriol has been found to be of clinical value in the treatment of dermatological disorders. This is considered to be safe with respect to alterations in calcium homeostasis. We report a 17-year-old female patient who developed hypercalcaemic crisis after excessive use of calcipotriol for ichthyosis. The clinical condition and serum calcium improved after cessation of calciprotiol treatment and rehydration with intravenous fluids and electrolytes. The case emphasizes the importance of limiting the topical use of calcipotriol as recommended by the manufacturer.

Amelioration of some pregnancy-associated variations in thyroid function by iodine supplementation

Knowledge of the effect of differences in iodine intake levels on public health in areas with no endemic goiter is limited. Groups at risk when iodine intake is relatively low are pregnant and lactating women and their newborns. A prospective randomized study was performed to evaluate the effect of iodine supplementation in an area where the median daily iodine excretion in urine is around 50 micrograms. Fifty-four normal pregnant women were randomized to be controls or to receive 200 micrograms iodine/day from weeks 17-18 of pregnancy until 12 months after delivery. In the control group, serum TSH, serum thyroglobulin (Tg), and thyroid size showed significant increases during pregnancy. These variations were ameliorated by iodine supplementation. Iodine did not induce significant variations in serum T4, T3, or free T4. Cord blood Tg was much lower when the mother had received iodine, whereas TSH, T4, T3, and free T4 levels were unaltered. The results suggest that a relatively low iodine intake during pregnancy leads to thyroidal stress, with increases in Tg release and thyroid size. However, the thyroid gland is able to adapt and keep thyroid hormones in the mother and the child normal, at least under normal circumstances, as evaluated in the present study. It is not known whether this stress is sufficient to be of importance for late development of autonomous thyroid growth and function.

[Radioiodine therapy of recurrent hyperthyroidism in patients previously treated for diffuse toxic goiter with subtotal surgery]

Radioiodine therapy is often employed for treatment of patients with relapse of hyperthyroidism due to Graves' disease, after previous thyroid surgery. Little is known about the outcome of this treatment compared to patients with no previous surgery. A total of 20 patients, who had received surgical treatment for Graves' hyperthyroidism 1-46 years previously and with relapse of hyperthyroidism, and 25 patients with hyperthyroidism due to Graves' disease and no previous thyroid surgery were treated with radioiodine, following the same protocol. Early after treatment the previously operated patients showed a higher sensitivity to radioiodine, with more cases of early hypothyroidism than non-operated patients. However, after 50 months of follow-up the outcome was identical. The results indicate that frequent assessment is necessary after radioiodine treatment of patients with previous thyroid surgery, since some patients develop early hypothyroidism.