Genotyping increases the accuracy of a clinical score (based on pretreatment age, goiter size, FT4, TBII) for predicting recurrence of Graves' hyperthyroidism after a course of antithyroid drugs: a prospective study.

The prevalence of TBII-seronegativity in untreated patients with GH is 5.4% using a second generation assay. TBII-seronegative patients have biochemically less severe thyrotoxicosis and no Graves' orbitopathy. TBII-seronegative and TBII-seropositive patients apparently belong to the same population of GH, albeit the severity of the autoimmune attack is less in TBII-seronegative patients.

Leptin administration selectively restores starvation-induced increased hepatic D3 expression independently of serum thyroid hormone concentrations. The present study shows that fasting-induced changes in mRNA expression of genes involved in hepatic hormone metabolism are influenced not only by decreased serum thyroid hormone levels but also by serum leptin.

Profound changes in thyroid hormone metabolism occur in the central part of the hypothalamus-pituitary-thyroid (HPT) axis during fasting. Hypothalamic changes are partly reversed by leptin administration, which decreases during fasting. It is unknown to what extent leptin affects the HPT axis at the level of the pituitary. We, therefore, studied fasting-induced alterations in pituitary thyroid hormone metabolism, as well as effects of leptin administration on these changes. Because refeeding rapidly increased serum leptin, the same parameters were studied after fasting followed by refeeding. Fasting for 24 h decreased serum T 3 and T 4 and pituitary TSHb, type 2 deiodinase (D2), and thyroid hormone receptor b2 (TRb2) mRNA expression. The decrease in D2 and TRb2 mRNA expression was prevented when 20 mg leptin was administered twice during fasting. By contrast, the decrease in TSHb mRNA expression was unaffected. A single dose of leptin given after 24 h fasting did not affect decreased TSHb, D2, and TRb2 mRNA expression, while 4 h refeeding resulted in pituitary D2 and TRb2 mRNA expression as observed in control mice. Serum leptin, T 3 , and T 4 after refeeding were similar compared with leptin administration. We conclude that fasting decreases pituitary TSHb, D2, and TRb2 mRNA expression, which (with the exception of TSHb) can be prevented by leptin administration during fasting. Following 24 h fasting, 4 h refeeding completely restores pituitary D2 and TRb2 mRNA expression, while a single leptin dose is ineffective. This indicates that other postingestion signals may be necessary to modulate rapidly the fasting-induced decrease in pituitary D2 and TRb2 mRNA expression.