Pituitary Thyroid Recovery following Surgery in TRH-Unresponsive Patients with Uni- and Multinodular Goiter

Eleven patients with single toxic nodular goiter (group A) had no TSH response to TRH (ΔTSH ≤ 1 µU/ml). Nine days after nodulectomy, TSH response was still absent in 10 patients. Responsiveness was delayed for between 2 and 7 weeks and was preceded by increases in serum T4 and T3 levels in two patients. TSH failed to respond to TRH in 11 single or multinodular goiter patients without thyroid hormone excess (group B). 9-12 days following removal of autonomously functioning tissue, 6 patients were still TRH resistant. Postoperative reversion to a positive TRH test was accompanied by a decrease in mean serum T4 concentration in the euthyroid range and by an increase in mean basal TSH level. The results suggest: (1) Return of TRH responsiveness is delayed following chronic thyroid hormone excess, even in the face of falling thyroid hormone levels. Eventual return of TRH responsiveness occurs when thyroid hormone levels have passed the postoperative nadir, suggesting that return of pituitary responsiveness is more critically dependent on time than on thyroid hormone levels. (2) During recovery of pituitary thyroid function, serum thyroid hormone values are more reliable than TSH reserve in defining the actual metabolic state. (3) Patterns of recovery of thyroid and thyrotropic function vary from patient to patient. (4) A slight decrease in endogenous thyroid hormone concentration well within the normal range reverts TSH response to normal in TRH-unresponsive euthyroid subjects.