Somatostatin inhibits thyroid hormone secretion induced by exogenous TSH in man.

The effect of somatostatin on thyroid hormone secretion stimulated by TSH in man was studied. The injection of TSH into a thyroid artery during surgery was followed by an increase in the serum concentration of iodothyronines in the corresponding thyroid vein. This increase was significantly lower (p less than 0.02) when somatostatin was given as a bolus injection into a peripheral vein 5 min prior to the administration of TSH, and followed by a continuous infusion for 60 min. Since somatostatin-like immunoreactivity has been localized to some cells of the thyroid gland being in a parafollicular location, it is suggested that somatostatin may be an intrathyroidal regulator of thyroid activity in man.