Rising serum thyroxine levels and chorea in graves' disease.

A 15-year-old girl presented with chorea as a first sign of Graves' hyperthyroidism. Chorea abated with antithyroid drug treatment and reappeared when hyperthyroidism recurred but not when thyrotropin receptor antibodies increased after administration of (131)I. Therefore, chorea in this patient is associated with hyperthyroxinemia and not with autoantibodies.

Reversible atrioventricular blocks in thyroid storm.

Atrioventricular blocks or sinoatrial blocks are rarely described in patients with thyrotoxicosis or thyroid storm. The mechanism of these blocks remains obscure. Thyroid storm, being an emergency situation requires early diagnosis and management because if left untreated, it may prove fatal. Usually patients with AV blocks require pacing (temporary or permanent). Here we describe a case who developed AV blocks, did not undergo pacing, but recovered only on antithyroid treatment.

Thyroid function in the nutritionally obese child and adolescent.

PURPOSE OF REVIEW: In recent years, there has been an increasing focus on thyroid function in obese children. There is controversy concerning whether the changes in the levels of thyroid hormones and thyroid-stimulating hormone (thyrotropin - TSH) in obesity are causes or consequences of weight status and whether these subtle differences merit treatment with thyroxine. This review aimed to study the prevalence of disturbed thyroid hormone and TSH values in childhood obesity and the underlying pathophysiologic mechanisms linking obesity to thyroid function. RECENT FINDINGS: In the past 18 months, four studies demonstrated moderate elevation of TSH concentrations in 10-23% of obese children, which was associated with normal or slightly elevated thyroxine and triiodothyronine values. Two studies reported ultrasonographic hypoechogenicity of the thyroid in obese children with hyperthyrotropinemia, which was not caused by autoimmune thyroiditis; therefore, the authors hypothesized a link to chronic inflammation in obesity. Weight loss led to a normalization of elevated TSH levels in two studies. The adipokine leptin is the most promising link between obesity and hyperthyrotropinemia since leptin stimulates the hypothalamic-pituitary-thyroid. SUMMARY: The elevated TSH levels in obesity seem a consequence rather than a cause of obesity. Therefore, treatment of hyperthyrotropinemia with thyroxine seems unnecessary in obese children.

Thyroid function and psychiatric morbidity in patients with manic disorder receiving lithium therapy.

Euthyroid hyperthyroxinemia as a result of a transient increase in thyroid-stimulating hormone (TSH) levels may contribute to the development of manic disorder. Lithium has a potent short-term antithyroidal effect that may account for its antimanic action. The thyroid function and psychiatric morbidity of 46 adult patients with manic disorder were assessed prospectively before and 1 and 6 months after lithium treatment. At baseline, the free thyroxine level (FT4, 16.23 +/- 3.11 pmol/L) was at the high end of the normal range, whereas the free triiodothyronine (FT3, 4.24 +/- 0.65 pmol/L) and TSH (1.47 +/- 0.73 mIU/L) levels were within the normal range. All patients were clinically euthyroid, but five of them (11%) had elevated FT4 levels. Baseline FT3 and FT4 levels were positively correlated with past psychiatric morbidity. The FT4 level at baseline and after 1 month of treatment was positively correlated with scores on the Brief Psychiatric Rating Scale (p < 0.02) and negatively correlated with scores on the Global Assessment Scale (p < 0.005). During the first month of treatment, the reduction of FT3 and FT4 levels was significantly correlated with a decrease in psychiatric symptoms. By 6 months, the FT3 level was no longer significantly different from that at the baseline, but FT4 levels remained significantly lower. The TSH level increased progressively from baseline to 6 months. Multilevel models showed that FT4 and serum lithium levels were positively and negatively associated with psychiatric symptoms, respectively. The findings of the study lend support to the notion that euthyroid hyperthyroxinemia contributes to acute mania and suggest that lithium's short-term antimanic action may be mediated by its antithyroid effect.

Thyroxine excess and pregnancy.

Pregnancy is characterised by a physiological increase in bound thyroxine but normal values of free hormone. Human chorionic gonadotrophin (hCG may stimulate the thyroid to produce hyperemesis gravidarum (with mild to moderate hyperthyroidism) or result in high thyroid hormone levels associated with gestational trophoblastic disease. Hyperthyroidism occurring during pregnancy is usually due to Graves' disease and must be treated to prevent congenital anomalies, low birth weight and premature labour. Thionamide drugs should be used with a preference for propylthiouracil (PTU) and continued in low doses up to labour. Breast feeding is possible in patients on low dose PTU. In the management of hypothyroidism during pregnancy thyroxine dose may require to be increased but excess dosage should be avoided because of its unwanted effects on foetal cerebral maturation. Neonatal hyperthyroidism due to transplacental passage of thyroid stimulating antibodies (TsAb) should be checked for in pregnant patients with autoimmune thyroid disease. As antithyroid drugs cross the placenta they may be used as therapy in this condition. Prevention of neonatal goitre is vital. Postpartum development of hyperthyroidism may be due to an exacerbation of pre-existing Graves' disease, development of new Graves' hyperthyroidism or postpartum thyroiditis with transient hyperthyroidism. Differentiation by measurement of TsAb and thyroidal iodine uptake is important because of therapeutic considerations.

Hyperthyroxinemia in major affective disorders.

Ninety-nine patients fulfilling DSM-III criteria for primary major affective disorder, either bipolar or unipolar, were studied. A 12% prevalence of elevated thyroxine levels was found. Three of the 12 hyperthyroxinemia patients also had elevated free thyroxine index. No statistically significant difference in response to antidepressant treatment was observed between the hyperthyroxinemia group and the normal serum thyroxine group.

Non-isotopic, two-step free thyroxine immunoassay: a better measure of free thyroxine than analogue radioimmunoassay.

Plasma or serum free thyroxine (T4) was measured by a novel non-isotopic, two-step immunoassay in 373 consecutive patients attending a thyroid clinic, in whom thyroid status was categorized according to clinical findings, supported by routine thyroid function tests. The 95% confidence limit of free T4 in the euthyroid patients (n = 112) was 7-20 pmol/L. Free T4 concentrations within the reference range were found in six of 40 patients with primary hypothyroidism and nine of 182 patients with overt thyrotoxicosis, six of whom had T3 toxicosis. Serum or plasma free T4 measured by the two-step method showed improved diagnostic specificity over an analogue RIA in selected groups of euthyroid patients in whom abnormal binding of analogue T4 can affect the validity of the result. Free T4 results found by analogue RIA and the two-step method in 58 patients who were receiving thyroxine replacement therapy were similar. The between-assay precision of the two-step method was poor ranging from a coefficient of variation of 9.7% to 19.3% over a free T4 concentration range of 5.0 to 46.0 pmol/L. We conclude that the two-step methodology offers diagnostic advantages for a laboratory which receives specimens from such patients for exclusion of thyroid disease but that improved assay precision is required before it could be used in a routine situation.