Neonatal thyroid disorders

Hypothyroxinaemia, which is common in the preterm infant, and thyrotoxicosis, which is rare, are important neonatal thyroid disorders. Their causes and treatment are discussed.

Does a homeopathic ultramolecular dilution of Thyroidinum 30cH affect the rate of body weight reduction in fasting patients? A randomised placebo-controlled double-blind clinical trial

OBJECTIVE

To test whether an ultramolecular dilution of homeopathic Thyroidinum has an effect over placebo on weight reduction of fasting patients in so-called 'fasting crisis'.

DESIGN

Randomised, placebo-controlled, double-blind, parallel group, monocentre study.

SETTING/LOCATION

Hospital for internal and complementary medicine in Munich, Germany.

SUBJECTS

Two hundred and eight fasting patients encountering a stagnation or increase of weight after a weight reduction of at least 100 g/day in the preceding 3 days.

INTERVENTION

One oral dose of Thyroidinum 30cH (preparation of thyroid gland) or placebo.

OUTCOME MEASURES

Main outcome measure was reduction of body weight 2 days after treatment. Secondary outcome measures were weight reduction on days 1 and 3, 15 complaints on days 1-3, and 34 laboratory findings on days 1-2 after treatment.

RESULTS

Weight reduction on the second day after medication in the Thyroidinum group was less than in the placebo group (mean difference 92 g, 95% confidence interval 7-176 g, P=0.034). Adjustment for baseline differences in body weight and rate of weight reduction before medication, however, weakened the result to a non-significant level (P=0.094). There were no differences between groups in the secondary outcome measures.

CONCLUSIONS

Patients receiving Thyroidinum had less weight reduction on day 2 after treatment than those receiving placebo. Yet, since no significant differences were found in other outcomes and since adjustment for baseline differences rendered the difference for the main outcome measure non-significant, this result must be interpreted with caution. Post hoc evaluation of the data, however, suggests that by predefining the primary outcome measure in a different way, an augmented reduction of weight on day 1 after treatment with Thyroidinum may be demonstrated. Both results would be compatible with homeopathic doctrine (primary and secondary effect) as well as with findings from animal research.

Periodontal 5'-deiodination on forced-induced root resorption--the protective effect of thyroid hormone administration

The present investigation was designed to study the protective effect given by thyroid hormone (TH) on root resorption: (1) whether intra-peritoneal versus oral TH administration had the same efficiency; and (2) whether this effect involved local or systemic mechanisms. For this purpose, circulating T3 levels, systemic alkaline phosphatase (APase) activity, and 5'deiodinase (5'D) activity were evaluated in the periodontal area of 80 Sprague-Dawley rats, 8 weeks of age, in which orthodontic appliances had been inserted. The results showed that TH-treated animals (intra-peritoneal or oral) had significantly less force-induced root resorptive lesions compared with a control group, without apparent changes in T3 or APase levels, and that periodontal remodelling was accompanied by a significant increase in local T3 generation as a result of T4 deiodination. This 5'D activity was higher in those animals that received exogenous TH. These results suggest that this protective TH mechanism may be achieved at a local level and that administration of low doses of TH may play a protective role on the root surface either during orthodontic treatment or in those patients that present spontaneous root resorptive lesions.

Evidence for a deficient pancreatic beta-cell response in a rat model of hyperthyroidism

To clarify mechanism behind the abnormal glucose tolerance, observed in hyperthyroidism, we studied genomic and nongenomic effects of thyroid hormone on insulin secretion using a rat model of hyperthyroidism. Male Sprague-Dawley rats were intraperitoneally injected with vehicle, low (100 microg/kg) or high dose (600 microg/kg) of thyroxin (T(4)) for 2 weeks. Rats treated with high dose, but not low dose, of T(4), showed an increase in serum T(3) levels, and a decrease in body weight as compared to control rats. In rats treated with either dose of T(4), fasting blood glucose levels were increased, but serum insulin levels were similar to those of controls. After an oral glucose load, blood glucose levels were increased in rats treated with high dose, but not low dose, of T(4). Serum insulin levels after the oral glucose load were decreased in rats treated with either dose of T(4). After an intravenous glucose load, blood glucose levels were comparable among groups, but serum insulin levels tended to be low in T(4)-treated rats. Steady-state blood glucose levels were comparable among groups. The insulin secretory responses to high glucose (20mM) or arginine (10mM) of the isolated pancreas was decreased in rats treated with high dose, but not low dose, of T(4). Mean insulin secretory response to glucose and arginine were decreased by 40.1% and by 60.4% in high-dose-T(4)-treated rats. Addition of T(3) in the perfusion medium decreased glucose-induced insulin release. Ratios of proinsulin mRNA levels to beta-actin mRNA were decreased in the islets of T(4)-treated rats (0.45 +/- 0.07 vs control 0.61 +/- 0.03, p < 0.05). Levels of TR (thyroid hormone nuclear receptor) alpha1 + cErb Aalpha2 mRNA, but not TRbeta1, were decreased in the pancreatic islets of T(4)-treated rats. Calculated islet area was increased, but the number of beta-cells determined immunohistochemically was not increased in T(4)-treated rats, nor the volume density of insulin positive islets. We concluded that a deficient pancreatic beta-cell response to glucose, rather than insulin resistance, was responsible for abnormal glucose tolerance in this model of hyperthyroidism. Thyroid hormone causes a decrease in glucose-induced insulin secretion. We observed nongenomic and genomic effects of thyroid hormone on glucose-induced insulin secretion.

Long-term consequences of congenital hypothyroidism in the era of screening programmes

Newborn screening for congenital hypothyroidism (CH), is one of the major achievements of medicine because early diagnosis and treatment has resulted in normal development in the vast majority of cases. However, all studies on outcome report up to 10% of patients with residual problems regarding mental development and neurological symptoms despite early diagnosis. Factors clearly associated with a less favourable outcome are late onset and an inadequate dosage of thyroid hormone substitution, a poor social-economic environment and compliance problems, while the impact of severity of CH at diagnosis on outcome is not completely settled, although most studies demonstrate a correlation between severity of hypothyroidism and poorer outcome. More recently in a few cases the molecular basis of CH has been clarified. It has become evident that, in some patients with persistent mental retardation and neurological symptoms, defects in transcription factors which are expressed in the thyroid gland as well as in the central nervous system (CNS) during embryonic development cause both defective thyroid and CNS development. The clarification of further molecular defects which affect the thyroid gland and brain development will help us to understand the poor outcome of patients with CH in the era of newborn screening and these diagnostic advances will ensure adequate counselling and care for these patients.

Postnatal thyroid hormone replacement in very preterm infants

Transient hypothyroxinemia occurs frequently in very preterm infants and is caused by a combination of factors as immaturity of the hypothalamo-pituitary-thyroid system, loss of the maternal thyroxine (T4) contribution, immaturity of thyroid hormone metabolism, and neonatal illness. Thyroid hormone is important in maturation of the brain, but also of heart and lungs. Low neonatal T4 concentrations in plasma are related to worse clinical and neurodevelopmental outcome. Despite these relationships, only few randomized clinical trials have been performed to find out whether T4 supplementation can improve clinical and/or neurodevelomental outcome of preterm infants. The currently available evidence does not support use of supplemental T4 in all preterm infants. There are, however, indications that T4 might improve neurodevelopmental outcome in infants born before 27 to 29 weeks of gestation. Therefore, it is necessary that new trials are set up to further study the benefits of thyroid hormones given in the neonatal period of very preterm infants.

Xerosis in hypothyroidism: a potential role for the use of topical thyroid hormone in euthyroid patients

Xerosis is an extraordinarily common problem in dermatology. Despite the knowledge of well recognized aggravating factors, its etiology is an enigma, and the management of the condition is often suboptimal. Dry skin may be a manifestation of hypothyroidism. The nature of this association is reviewed, culminating in the speculation that topical thyroid hormone may represent a useful modality in euthyroid patients with xerosis or other disorders of keratinization.

Treatment of hypothyroidism

Thyroid disease affects up to 0.5 percent of the population of the United States. Its prevalence is higher in women and the elderly. The management of hypothyroidism focuses on ensuring that patients receive appropriate thyroid hormone replacement therapy and monitoring their response. Hormone replacement should be initiated in a low dosage, especially in the elderly and in patients prone to cardiac problems. The dosage should be increased gradually, and laboratory values should be monitored six to eight weeks after any dosage change. Once a stable dosage is achieved, annual monitoring of the thyroid-stimulating hormone (TSH) level is probably unnecessary, except in older patients. After full replacement of thyroxine (T4) using levothyroxine, the addition of triiodothyronine (T3) in a low dosage may be beneficial in some patients who continue to have mood or memory problems. The management of patients with subclinical hypothyroidism (a high TSH in the presence of normal free T4 and T3 levels) remains controversial. In these patients, physicians should weigh the benefits of replacement (e.g., improved cardiac function) against problems that can accompany the excessive use of levothyroxine (e.g., osteoporosis).

Augmentation of standard depression therapy

OBJECTIVE

This article reviews treatment options (eg, augmentation) for depressed patients with suboptimal clinical responses to an antidepressant.

BACKGROUND

Approximately one third of patients treated with antidepressants exhibit suboptimal or delayed clinical response to these medications. In such cases, alternative options include switching to another antidepressant or adding a second antidepressant. Augmentation strategies include addition of lithium carbonate, atypical antipsychotics, psychostimulants, thyroid hormone (triiodothyronine), pindolol, or buspirone.

CONCLUSIONS

In approximately half of all antidepressant-resistant cases of major depressive disorder, controlled clinical trials have indicated that augmentation with lithium or thyroid hormone is effective. Other reports suggest that central nervous system stimulants may augment antidepressant activity, but their use is constrained by possible abuse potential. Pindolol therapy has been shown to accelerate clinical response in some but not all studies. Finally, the favorable safety and tolerability profile of buspirone, together with its desirable anxiolytic effects, render it a sound therapeutic option in antidepressant augmentation.

Concomitant medication use in postmenopausal women using estrogen therapy

OBJECTIVE

To determine whether long-term postmenopausal estrogen therapy is associated with use of other prescription medications.

METHODS

Using computer pharmacy records from 1969 to 1973 for members of the Kaiser Permanente Medical Care Program in San Francisco, we identified the 215 most commonly used prescription medications in the pharmacy database and recorded their use by 232 postmenopausal long-term estrogen users and by 222 postmenopausal age-matched nonusers. These medications were grouped into 39 therapeutic classes. Classes of medications used by estrogen users and nonusers were compared.

RESULTS

A statistically significant difference in use was seen for 21 of the 39 medication classes; of these 21 classes, 20 (95%) were used more frequently and 1 less frequently by estrogen users. Differences between estrogen users and nonusers were greatest for thyroid hormone preparations (estrogen user/nonuser multivariate odds ratio = 25.6, 95% confidence interval 5.9-112) and antimigraine preparations (11 recipients among estrogen users, none among nonusers). Postmenopausal women using estrogen were more likely than nonusers to use additional medications.

CONCLUSION

Greater use of certain prescription medications by estrogen users than by nonusers should be considered in studying the health effects of estrogen replacement therapy.

Hydroxypropyl-beta-cyclodextrin as delivery system for thyroid hormones, regulating glutathione S-transferase expression in rat hepatocyte co-cultures

Thyroid hormones play a role in the regulation of glutathione S-transferase (GST) expression. Here, co-cultures of rat hepatocytes with bile duct epithelial cells have been used to study the direct effects of both triiodothyronine (T3) and thyroxine (T4) on GST activities and proteins. Because T3 and T4 are poorly water soluble and organic solvents used to dissolve them often interfere with biotransformation pathways, an alternative delivery system namely hydroxypropyl-beta-cyclodextrin (HPBC) has been applied. Appropriate control cultures contained either 0.02 or 0.10% (w/v) HPBC, the concentrations necessary to supply T3 and T4 (10(-9) to 10(-5) M) to the cells, respectively. No effect of the vehicle HPBC on the different GST isoenzyme activities and proteins could be observed. On the contrary, after 10 days of co-culture, T3 and T4 decreased GST protein concentrations as well as GST activities measured by 1-chloro-2,4-dinitrobenzene (broad spectrum), 1,2-dichloro-4-nitrobenzene (Mu class M1/M2-specific) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (Alpha class A1/2-specific) in a concentration-dependent manner. The Alpha class subunits A1/2 and A3, and the Mu class subunit M2 were mostly affected. No effect was observed on the Pi class enzyme. These findings indicate that a combination of co-cultured hepatocytes with an HPBC-based delivery system for hydrophobic compounds represents a powerful in vitro tool in drug development.

Preparation by recombinant human thyrotropin or thyroid hormone withdrawal are comparable for the detection of residual differentiated thyroid carcinoma

Clinical recurrences of differentiated thyroid carcinoma occur in 20% of patients after thyroid surgery. We performed a retrospective analysis of a cohort of patients undergoing routine follow-up testing to detect recurrent thyroid carcinoma over a 2-yr period. One group was prepared for testing by thyroid hormone withdrawal (THW), and the other group remained on thyroid hormone and received injections of recombinant human TSH (rhTSH) before diagnostic whole-body radioiodine scanning (DxWBS). We hypothesized that no differences in the ability to detect residual disease would exist between these 2 groups. Two hundred and eighty-nine patients were examined by both DxWBS and by measurement of the serum thyroglobulin (Tg) response to elevated TSH levels. THW was used for 161 patients, and rhTSH preparation was used for 128 patients. Based on all available testing results, we categorized patients as having metastatic disease, thyroid bed uptake only, or no evidence of disease. We examined the sensitivity, specificity, positive and negative predictive values of the DxWBS, and the stimulated Tg after preparation by THW or rhTSH. Patients with thyroid bed were not considered in accuracy testing. The sensitivity and specificity of the 2 tests were comparable between groups. No significant differences were present in the positive or negative predictive values between groups. The highest negative predictive value (97%) was in patients who had both a negative DxWBS and low stimulated Tg levels after rhTSH. In summary, we were unable to demonstrate a difference in the diagnostic accuracy of DxWBS and/or Tg between patients prepared by either THW or rhTSH. We conclude that preparing patients by rhTSH is diagnostically equivalent to preparing them by THW.

Antidepressant augmentation and combinations

A significant proportion of patients with MDD are treatment resistant or only partial responders to adequate therapy with a single agent. In this situation, one must consider augmentation with another agent. Lithium and thyroid augmentation have been investigated for many years. In a meta-analysis of double-blind studies involving augmentation with lithium or placebo after nonresponse to conventional antidepressants, lithium augmentation was concluded to be the first-line therapy for depressed patients who failed to respond to monotherapy. One important study reported no significant difference in response rates between T3 and lithium as augmentation agents in patients who had failed to respond to TCAs. Very few controlled, double-blind trials show consistently positive results for the other augmentation strategies, although some open-labeled trials and case reports are promising. Additional placebo-controlled, double-blind studies are needed to assess the efficacy and tolerability of all of these agents, especially in combination with the newer classes of antidepressants.

Is excessive weight gain after ablative treatment of hyperthyroidism due to inadequate thyroid hormone therapy?

There is controversy about the correct dose and form of thyroid hormone therapy for patients with hypothyroidism. Despite restoration of serum thyrotropin (TSH) concentrations to normal, many patients complain of excessive weight gain. We have compared weight at diagnosis of hyperthyroidism with that when euthyroid, evidenced by a stable, normal serum TSH concentration, with or without thyroxine (T4) replacement therapy, in patients treated with an 18-month course of antithyroid drugs (43 patients), surgery (56 patients), or 13I (34 patients) for Graves' disease. In addition, weights were recorded before and after treatment of 25 patients with differentiated thyroid carcinoma by total thyroidectomy, 131I, and long-term T4 suppressive therapy, resulting in undetectable serum TSH concentrations. Mean weight gain in patients with Graves' disease who required T4 replacement therapy following surgery was significantly greater than in those of the same age, sex, and severity of hyperthyroidism rendered euthyroid by surgery (3.9 kg) (p < 0.001) or at the end of a course of antithyroid drugs (4.1 kg) (p < 0.001). Weight gain was similar in those requiring T4 replacement following surgery or 131T therapy (10.4 versus 10.1 kg). In contrast, ablative therapy combined with suppression of TSH secretion by T4 in patients with differentiated thyroid carcinoma did not result in weight gain. The excessive weight gain in patients becoming hypothyroid after destructive therapy for Graves' disease suggests that restoration of serum TSH to the reference range by T4 alone may constitute inadequate hormone replacement.

[Surgical treatment of recurrent goiter]

The authors have analyzed and generalized their 20-years experience with surgical treatment of 247 patients with recurrent goiter. Among them 48 patients had recurrent toxic goiter and 199 patients had nontoxic goiter. Postoperative complications developed in 8.3% of the patients with recurrent toxic goiter and in 6% of the patients with nontoxic goiter. The overall postoperative lethality was 1.2%. Operative treatment is recommended by the authors for recurrent toxic and nontoxic goiter, conservative treatment with radioactive iodine is thought to be expedient for a repeated recurrence. For preventing recurrences of toxic and nontoxic goiter after the first operation the administration of small does of the thyroid hormones is considered to be expedient during 1.5-2 months.

Optimal strategy for management of pituitary disease in the growth hormone-deficient teenager

The optimal treatment of chronic conditions spanning pediatric and adult clinical practice requires the establishment of clear and robust systems for managing the important period of transition of care. This principle is particularly relevant to the treatment of ongoing pituitary dysfunction after the achievement of final height and, in addition to the vital component of maintaining the confidence of the patient, encompasses a number of considerations that are particularly relevant to long-term health as an adult. These considerations include the achievement of peak bone mass, optimization of gonadal steroid and glucocorticoid replacement, and determination of the need for continuing growth hormone replacement. It is therefore necessary to consider these issues not only from the standpoint of therapeutic principles but also in the context of practical arrangements for managing the process of transition of care. Successful transition can be achieved using a variety of models, and there is clearly no single preferable option. The most important ingredient in this process is awareness of the situation by both pediatric and adult endocrinologists as well as the development of an agreed strategy within each clinical center.

Long-term neuropsychological sequelae of early-treated congenital hypothyroidism: effects in adolescence

A cohort of over 100 children with congenital hypothyroidism (CH) detected via newborn screening was followed regularly throughout childhood and into adolescence. They were studied using a variety of different tests as part of three consecutive research components: semiannual/annual psychological assessments using age-appropriate intelligence tests (phase I), detailed psychoeducational evaluations in grades 3 and 6 (phase II) and a thorough neuropsychological evaluation during adolescence (phase III). Controls for phase I were siblings and for phase II, classmates and siblings. Phase III controls were drawn from a larger control pool and were individually matched with each CH case for age and gender. The results showed that although the CH group was intellectually functioning well within the normal range by adolescence, the children were performing significantly below expectation. Longitudinal analyses showed significant declines in IQ with age, signifying that the CH group was failing to make the same age-related gains as controls. Children with CH showed significantly poorer performance in visuospatial, language and fine motor areas as well as selective attention and memory deficits. At school, they were initially below par in arithmetic but were able to catch up by grade 6; however, their teachers reported that they were not performing as well as controls in the classroom and they demonstrated more difficulty with more complex school subjects such as science and social studies. Correlational analyses indicated different manifestations of early hypothyroidism versus later treatment factors, suggesting that while some effects can be improved by better treatment and management approaches, others caused by prenatal and perinatal thyroid hormone insufficiency may persist.

Reproductive and hormonal risk factors for thyroid cancer in Los Angeles County females

We conducted an individually matched case-control study (292 pairs) of female thyroid cancer patients to examine the role of reproductive history and exogenous hormones in this disease. Radiation treatment to the head or neck [28 cases and 2 controls exposed; odds ratio (OR), 14.0; 95% confidence interval (CI), 3.5-121.3] and certain benign thyroid diseases (including adolescent thyroid enlargement, goiter, and nodules or tumors) were strongly associated with thyroid cancer. Irregular menstruation increased risk (OR, 1.8; 95% CI, 0.9-3.7). Age at menarche and pregnancy history were not related to disease. Women with natural menopause and hysterectomized women without oophorectomy had no increase in risk, but disease risk was elevated in women with bilateral oophorectomy (OR, 6.5; 95% CI, 1.1-38.1). In general, use of oral contraceptives and other exogenous estrogens was not associated with thyroid cancer. However, risk increased with number of pregnancies in women using lactation suppressants (P = 0.03) and decreased with duration of breastfeeding (P = 0.04). These data provide only limited support for the hypothesis that reproductive and hormonal exposures are responsible for the marked excess of thyroid cancer risk in adult females.

A comparison of recombinant human thyrotropin and thyroid hormone withdrawal for the detection of thyroid remnant or cancer

Recombinant human TSH has been developed to facilitate monitoring for thyroid carcinoma recurrence or persistence without the attendant morbidity of hypothyroidism seen after thyroid hormone withdrawal. The objectives of this study were to compare the effect of administered recombinant human TSH with thyroid hormone withdrawal on the results of radioiodine whole body scanning (WBS) and serum thyroglobulin (Tg) levels. Two hundred and twenty-nine adult patients with differentiated thyroid cancer requiring radioiodine WBS were studied. Radioiodine WBS and serum Tg measurements were performed after administration of recombinant human TSH and again after thyroid hormone withdrawal in each patient. Radioiodine whole body scans were concordant between the recombinant TSH-stimulated and thyroid hormone withdrawal phases in 195 of 220 (89%) patients. Of the discordant scans, 8 (4%) had superior scans after recombinant human TSH administration, and 17 (8%) had superior scans after thyroid hormone withdrawal (P = 0.108). Based on a serum Tg level of 2 ng/mL or more, thyroid tissue or cancer was detected during thyroid hormone therapy in 22%, after recombinant human TSH stimulation in 52%, and after thyroid hormone withdrawal in 56% of patients with disease or tissue limited to the thyroid bed and in 80%, 100%, and 100% of patients, respectively, with metastatic disease. A combination of radioiodine WBS and serum Tg after recombinant human TSH stimulation detected thyroid tissue or cancer in 93% of patients with disease or tissue limited to the thyroid bed and 100% of patients with metastatic disease. In conclusion, recombinant human TSH administration is a safe and effective means of stimulating radioiodine uptake and serum Tg levels in patients undergoing evaluation for thyroid cancer persistence and recurrence.

The effect of thyroid hormone on skeletal integrity

BACKGROUND

Thyroid disease and osteoporosis are common problems often managed by primary care physicians. Despite many studies, confusion still exists about the effect of thyroid hormone on skeletal health.

PURPOSE

To review evidence on the effect of thyroid hormone (from hyperthyroidism, exogenous or endogenous suppression of thyroid-stimulating hormone [TSH], and thyroid hormone replacement therapy) on skeletal integrity.

DATA SOURCES

A MEDLINE search of papers published between 1966 and 1997.

DATA SELECTION

Cross-sectional studies, longitudinal studies, and meta-analyses that had appropriate control groups (patients matched for age, sex, and menopausal status), made comparisons with established databases, or defined thyroid state by TSH level or thyroid hormone dose were reviewed.

DATA EXTRACTION AND SYNTHESIS

Data synthesis was not straightforward because of changes in doses and types of thyroid hormone preparations; changes in definitions of thyroid hormone replacement therapy and suppressive therapies; problems with study design; differences in skeletal sites assessed (hip, spine, forearm, or heel) and techniques used to measure bone mineral density; and inclusion of heterogenous and changing thyroid disease states. Overall, hyperthyroidism and use of thyroid hormone to suppress TSH because of thyroid cancer, goiters, or nodules seem to have an adverse effect on bone, especially in postmenopausal women; the largest effect is on cortical bone. Thyroid hormone replacement seems to have a minimal clinical effect on bone.

CONCLUSION

Women with a history of hyperthyroidism or TSH suppression by thyroid hormone should have skeletal status assessed by bone mineral densitometry, preferably at a site containing cortical bone, such as the hip or forearm.

Outcome of treatment of hyperthyroidism

This is a retrospective study designed to evaluate the initial response to carbimazole in patients with Graves' disease (GD), possible determinants of that response, the frequency of occurrence of adverse effects during treatment with carbimazole and the frequency of transient and permanent hypothyroidism after treatment with 131I in patients with GD and multinodular goiter (MNG). Data were collected from patients who first presented with GD or MNG at the Department of Endocrinology of the Royal Infirmary of Edinburgh between 1 January 1993 and 31 August 1996. Patients were divided into three groups: patients with GD treated with a daily dose of 40 mg carbimazole, patients with GD treated with a single dose of 400 MBq 1311, and patients with MNG treated with the same dose of 131I. Of the patients younger than 30 years, 50% remained biochemically hyperthyroid after 4-6 weeks of treatment with carbimazole, compared to 14% of patients over 30. Other determinants of the response to carbimazole expressed as the fall in thyroid hormone levels after 4-6 weeks were: pretreatment levels of FT4, T3, TRAb and the 4 h 131I uptake, patients with the higher levels responding significantly better to carbimazole. Adverse effects were reported in 11.5% of patients. Of the patients with GD treated with 1311, 62.6% became hypothyroid, transient hypothyroidism occurred in only 2.4% of these cases. The main predictors of development of hypothyroidism were positive titres of antithyroid peroxidase antibodies (AbTPO) and antithyroglobulin antibodies (AbTg), with positive predictive values of 79.5 and 91.6 respectively. None of the patients with MNG became hypothyroid after treatment with 131I, a response significantly different from patients with GD. In conclusion, GD younger patients might benefit from higher initial doses of carbimazole. In patients with positive titres of AbTPO and AbTg, lower doses of 1311 might prevent hypothyroidism. Transient hypothyroidism was underestimated in this study. No permanent thyroxin replacement therapy should be started within the first six months after 131I treatment.