Hypothyroidism-induced hyperprolactinemia, with or without clinical manifestations, is reported in a short case in addition to the results of basal and thyrotropin-releasing hormone (TRH)-induced prolactin values in primary hypothyroidism. In comparison with an age- and sex-matched group, basal- (P less than 0.02) and TRH-induced (P less than 0.02) prolactin values are significantly increased in primary hypothyroidism. A review of the literature and the possible pathogenesis of hyperprolactinemia, amenorrhea and galactorrhea are discussed. No correlation could be found between maximal thyrotropin (TSH) and prolactin-increase values.