Practice guidelines for the detection and management of thyroid dysfunction. A comparative review of the recommendations

Pericardial effusion in severe hypothyroidism in children

Pleural and pericardial effusion is a rare complication of severe hypothyroidism in children but can be present in 10 to 30% of adults. Most pediatric cases have been in children with Down syndrome. In this report, six cases of pericardial effusion in children with severe hypothyroidism with and without trisomy 21 are presented. In all patients, the pericardial effusion was managed successfully without pericardiocentesis. The effusions resolved completely in 2 to 12 months after initiation of thyroxin replacement. In conclusion, hypothyroidism should be considered in any child with unexplained pericardial or pleural effusions. Early recognition and treatment with thyroid hormone replacement could eliminate the need for unnecessary diagnostic procedures and invasive treatment measures and reduce the risk of progression to cardiac tamponade.

The management of subclinical hyperthyroidism by thyroid specialists

Subclinical hyperthyroidism is a relatively common condition for which prospectively derived evidenced-based management guidelines do not exist. We have conducted a case-based mail survey to solicit opinions from members of the American Thyroid Association (ATA) about various issues that arise in the management of patients with this disorder. The survey was completed and returned by 185 of 300 (62%) of the original survey recipients. Four hypothetical cases varying in age, thyrotropin (TSH) level and underlying etiology were presented. The majority of respondents recommended further evaluation of all cases, most commonly choosing a radioactive iodine uptake (42%-71%), thyroid scan (39%-68%) and antithyroid (TPO/Tg) antibodies (49%-55%) as the additional tests to be ordered. The large majority (84%) recommended observation rather than active treatment for a young patient with a low but detectable serum TSH level. A small majority also recommended observation alone for a young woman with an undetectable serum TSH level (58%) and for an older woman with a low but detectable serum TSH value (63%). However, the majority (66%) favored treating an older woman with an undetectable serum TSH. When treatment was advised in the patients with subclinical hyperthyroidism, the respondents strongly favored anti-thyroid drugs when the etiology was Graves' disease and radioactive iodine when the etiology was toxic nodular thyroid disease. In the absence of adequate evidence-based guidelines, it is hoped that this survey of expert opinions may provide useful guidance for physicians providing care for patients with subclinical hyperthyroidism.

A multicenter cluster randomized controlled trial of strategies to improve thyroid function testing

OBJECTIVES

This project aimed to compare the independent and combined effectiveness of two implementation interventions of guidelines for ordering thyroid function tests: a Memorandum Pocket Card (MPC) and a Test Request Form (TRF).

RESEARCH DESIGN

Intervention groups were wards. The study used an experimental 2*2 factorial design with matching hospitals according to size and activity and wards according to preintervention appropriateness for test ordering. Four ward groups were established: the dual intervention group, the order form group, the pocket card group and the control group. Physicians in all groups received guidelines and were invited to a local information meeting.

MEASURES

The main outcome measure of effectiveness was the Guideline Conformity Rate (GCR).

RESULTS

Six hospitals participated in the study (two middle-sized hospitals, two small-sized hospitals and two psychiatric hospitals). A total of 1412 orders for thyroid function tests were collected. GCR was 78% in the dual intervention group, 83% in the order form group, 73% in the pocket card group and 62% in the control group. The interaction between TRF and MPC was not significant (beta = -0.70; P = 0.21). Compared with simple information, TRF was effective in increasing GCR (OR, 2.65; 95% CI, 1.52-4.62), unlike MPC (OR, 1.28; CI, 0.75-2.19).

CONCLUSIONS

Using a robust design, our study shows the greater effectiveness of TRF than MPC and their association in implementing thyroid function test guidelines.

Subclinical hypothyroidism in obese patients: relation to resting energy expenditure, serum leptin, body composition, and lipid profile

OBJECTIVE

To evaluate whether subclinical hypothyroidism (SH) affects resting energy expenditure (REE) as well as body composition, lipid profile, and serum leptin in obese patients.

RESEARCH METHODS AND PROCEDURES

A total of 108 obese patients with SH defined as normal free thyroxine levels and thyroid-stimulating hormone (TSH) values of > 4.38 microU/ml (mean +/- 2 SD of the values of our reference group of obese patients with normal thyroid function) were compared with a group of 131 obese patients matched for age, sex, and body mass index (BMI) but with normal TSH levels. We assessed estimated daily caloric intake by 7-day recall, REE by indirect calorimetry, body composition by bioelectrical impedance analysis, serum leptin by radioimmunoassay, and lipid profile (i.e., total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides).

RESULTS

All of the variables measured were not different between the euthyroid obese patients and those with SH. In a multiple regression model with REE expressed for kilograms of fat free mass (REE/kgFFM) as a dependent variable and percentage of fat mass, BMI, waist-to-hip ratio, age, TSH, free thyroxine, serum leptin, and caloric intake as independent variables, only percentage of fat mass was significantly correlated with REE/kgFFM in both groups. In the SH group only, BMI, waist-to-hip ratio, age, and TSH were related to REE/kgFFM and explained 69.5% of its variability. After dividing the patients with SH using a cutoff TSH value of 5.7 microU/ml, which represents 3 SD above the mean of TSH levels of the group of obese patients with normal thyroid function, only REE/kgFFM was significantly different and lower in the group of more severely hypothyroid patients.

DISCUSSION

In patients with obesity, SH affects energy expenditure only when TSH is clearly above the normal range; it does not change body composition and lipid profile. We suggest that, at least in obese patients, evaluation of TSH levels may be useful to rule out a possible impairment of resting energy expenditure due to a reduced peripheral effect of thyroid hormones.

Hypothyroidism and aging: the Rosses' survey

An earlier impression of a high prevalence of hypothyroidism in a general practice (4,190 patients including 1,544 adult females aged 18 years or more with 544 aged 50 years or more) in the Rosses, a coastal area in the northwest of Ireland was confirmed by this study. The accumulated prevalence of overt spontaneous primary hypothyroidism was 8.6% in 544 females aged 50 years or more but only 0.9% in the 1,000 females between 18 and 50 years of age. This prevalence was approximately twice that of an Irish National general practice population sample of 4,314 females aged 50 years or more (8.6% vs. 4.6%) p < 0.001. The reasons for this difference are unclear but may reflect the high level of opportunistic screening carried out in West Donegal. Thyroid peroxidase antibodies measured by radioimmunoassay were found in 75.6% of hypothyroid patients compared to 18.6% of practice controls (p < 0.01). Neither HLA-DRB1, DQA1, and DQB1 phenotype frequencies nor dietary iodine intake (median urinary iodine excretion 104 microg/L) appeared to be contributory factors. The finding of an 8.6% accumulated prevalence of hypothyroidism in females greater than 50 years of age when a population is aggressively investigated demonstrates the relative importance of its contribution to total morbidity and suggests that the disorder may be underdiagnosed, thus supporting the concept of targeted screening in this age group.

Disorders of thyrotropin synthesis, secretion, and function

Advances related to thyrotropin during 1999 included better understanding of the genetic basis of pituitary development and genetic advances in identifying clinical entities and their mechanisms and enabling new therapies. Initial clinical use of recombinant thyrotropin in evaluation of thyroid cancer recurrence was described. The importance of glycosylation pattern was clarified including the role of thyrotropin-releasing hormone in synthesis of thyrotropin molecules with mature glycosylation, and the impact of abnormal glycosylation in loss-of-function and gain-of-function mutations of the thyrotropin receptor. Causes of excessive thyrotropin secretion were evaluated, including pituitary thyrotropin-secreting adenomas. The fairly common causes of central hypothyroidism including ischemic injury, cranial irradiation, psychiatric conditions, or medical illness were assessed. The action of thyrotropin at the thyroid cell was assessed as a growth factor and as an influence on tyrosine sulfate content of thyroglobulin. Such basic and clinical science advances are rapidly affecting clinical care.

Disclosing subclinical thyroid disease. An approach to mild laboratory abnormalities and vague or absent symptoms

Patients with subclinical thyroid disease often have no apparent symptoms or only nonspecific complaints. However, increasing evidence that early disease is associated with behavioral, psychiatric, biochemical, and organ-specific abnormalities has led several specialty organizations to publish or modify position papers. Serum TSH testing is the most sensitive method of identifying early thyroid dysfunction. It should be considered in patients who have risk factors for mild thyroid failure, have symptoms that could be related to thyroid disease, or are taking exogenous thyroid hormone. T4 therapy should be strongly considered in patients with a TSH level of 10 mIU/L or more. If observation is elected in asymptomatic patients with lesser TSH elevation, periodic measurements are advised. In patients with TSH suppression who are taking thyroid hormone, the dose should be lowered. If the TSH level is decreased because of endogenous suppression and free-T4 and T3 levels are normal, options include observation and treatment with an antithyroid drug or thyroid ablation. Early therapy should be considered in older patients and those with heart disease or nodular thyroid disease. The goal of all treatment methods should be to keep the TSH level in the normal range.