Lack of effect of somatostatin on thyroid gland function in Graves' disease

Five women with Graves' disease, 26-52 years of age, with serum concentrations of triiodothyronine (T3) 4.8-9.2 nmol/l and thyroxine (T4) 200-320 nmol/l were studied. A 26 h infusion of cyclic somatostatin (Bachem), 6 mg in isotonic saline solution was administered. Radioactive iodine i.v. (125I or 131I) was given immediately after the start of this infusion. Serum T3, T4 and conversion rate (CR% = PBRI: total RI X 100) were determined four times during the infusion, then daily for a week. The same studies, related to an injection of radioiodine, were performed during a control week when no somatostatin was administered. Arginine-stimulated insulin and growth hormone (hGH) concentrations were considerably lowered by the somatostatin infusion. No difference in serum T3, T4 or CR between the week that started with somatostatin infusion and the control week was observed. Twelve-26 h after the somatostatin infusion started, all patients experienced gastrointestinal symptoms, which lasted 2-6 h after somatostatin withdrawal. Somatostatin in the dose given does not inhibit thyroid gland function in Graves' disease.