Sporadic non-toxic goitre: an investigation of the hypothalamic-pituitary-thyroid axis.

Thyrotrophin releasing hormone (TRH) tests have been carried out on sixty-two patients with sporadic non-toxic nodular goitre. 61% gave a subnormal thyroid stimulating hormone (TSH) response but had normal plasma thyroxine (T4) and triiodothyronine (T3) levels. T3 administration suppressed 131I uptake by the thyroid adequately in 74% of these and there was normal stimulation of thyroid uptake by exogenous TSH. Prolactin (PRL) rose normally after TRH in all the TRH non-responders. Normal TSH response to TRH was restored by partial thyroidectomy and in some cases by propyl thiouracil administration. Possible reasons for these findings are discussed. It is concluded that these cases were truly euthyroid.