Inhibition by somatostatin of mouse thyroid activity following stimulation by thyrotrophin, isoprenaline and dibutyryl cyclic-AMP.

The recent discovery of somatostatin-containing cells within the thyroid gland infers that somatostatin may influence thyroid activity. This possibility was investigated by measurements of radio-iodine release in mice pre-treated with 125I and T4. The animals were treated with TSH, isoprenaline or dibutyryl-cyclic AMP with and without concomitant injection of somatostatin. It was found that somatostatin reduced the blood 125I increase in response to each of the three thyroid-stimulating agents. The elimination rates of 125I-labelled T4 and T3 were unaffected by somatostatin. The observations suggests that somatostatin may participate in the regulation of thyroid hormone secretion, by an inhibitory effect exerted within the thyroid gland.