TIAPRIDE-INDUCED CHRONIC HYPERPROLACTINAEMIA: INTERFERENCE WITH THE HUMAN MENSTRUAL CYCLE

Publisher Website
Google Scholar
Abstract
Four regularly menstruating volunteers were treated orally with tiapride [daily doses from 100-200 mg] for 3 consecutive cycles, starting on the 1st day of a cycle. The 1st and the last cycle under treatment, as well as a prior control cycle, were thoroughly studied by means of daily measurements of blood concentrations of LH [lutropin], FSH [follitropin], prolactin (PRL), estradiol and progesterone. Tiapride, a benzamide derivative with dopaminergic blocking activity at the level of the lactotrophs, increased mean PRL secretion in each subject but a permanent hyperprolactinemia above 700 .mu.U[units]/ml was attained only in 1 subject. Despite these widely fluctuating PRL levels in most subjects, the resulting overall hyperprolactinemia induced in all cases a progressive deterioration of the function of the corpus luteum; 5 cycles showed luteal phases reduced by 2-5 days; 1 cycle was characterized by some slight luteinization but questionable ovulation; and the 2 remaining cycles were anovulatory. The interruption of drug intake 1 wk after the onset of menses led thereafter to a cycle with a likely inadequate luteal phase but of normal length. Even a non-permanent hyperprolactinemia can impair the normal function of the hypothalamo-pituitary-ovarian axis and exhibit some effects in a cycle consecutive to the normalization of PRL. With the exception of the impaired luteal progesterone secretion, the pooled hormonal data from the short luteal phase cycles under tiapride-induced hyperprolactinemia exhibit very little significant differences, as compared to the the corresponding values in the control cycles. Some delay in the onset of follicular maturation, however, should be assumed since the follicular phase had been lengthened by 1-31 days in 5 of the 6 cycles with luteinization during treatment. The present results are compatible with a double impact-both at the ovarian and the hypothalamo-pituitary levels-of hyperprolactinemia in its mechanisms of impaired function of the hypothalamo-pituitary ovarian axis.