Cimetidine induced prolactin (PRL) release in thyroid disease.

Effects of acute intravenous administration of cimetidine on serum levels or PRL, TSH, LH and FSH were investigated in six healthy euthyroid, five hypothyroid and five hyperthyroid patients. Cimetidine failed to alter serum TSH levels in the hypothyroid patients. There was no change in LH and FSH levels except in two euthyroid subjects in whom significant rise in LH occurred. However, in all subjects, whether euthyroid, hypo- or hyperthyroid, the serum PRL concentration increased two to three fold above basal levels. The peak levels of serum PRL occurred at 15 min following the drug administration. The response was not blunted in the older age group. We conclude that unlike the TRH-mediated PRL release, the cimetidine-induced PRL release is independent of the levels of thyroid hormone.