Thyrotropin-releasing hormone stimulation of thyrotropin secretion is suppressed by calcium ion antagonists that block transmembrane influx and intracellular mobilization of calcium ion in human subjects

Thyroid status and hepatic thyroxine deiodinating activity under high-dose long-term nitrendipine

The influence of high doses of oral nitrendipine on the hypophyseal-thyroid axis and on peripheral thyroxine metabolism was studied in baboons. Administration of 320 mg oral nitrendipine per kg body weight (b.wt.) for three months caused a hypothyroid state with decreased values for thyroxine and reverse triiodothyronine, elevated TSH, but unchanged triiodothyronine; the lower doses investigated (24 and 48 mg/kg b.wt.) were without any effect. High doses of nitrendipine concomitantly increased hepatic 5'-deiodinating activity by a rise in Vmax, which could be attributed to an increase in the deiodinating enzyme content. Normal T3 serum levels in the presence of low T4 serum concentrations under high dose nitrendipine can be ascribed, at least in part, to the enhanced peripheral 5'-deiodination.

Nimodipine in migraine: clinical efficacy and endocrinological effects

Serum prolactin is increased during chronic flunarizine treatment of patients suffering from migraine. In order to clarify the role of calcium in control of the secretion of anterior pituitary hormones, a study has now been made of the effects of chronic nimodipine and propranolol treatment of migraine patients on prolactin (PRL), luteinizing hormone (LH) and growth hormone (GH) levels. 11 patients were treated with nimodipine and 8 with propranolol for four months. A statistically significant reduction in the frequency of the attacks was demonstrated in both groups. No significant change was found in the hormones levels during nimodipine treatment.