The aetiology of galactorrhoea in women with regular menstruation and normal prolactin levels.

Fourteen primary infertile women with expressible galactorrhoea associated with regular ovulatory cycles and normal basal prolactin levels (group A) were matched for age and weight with 14 infertile women with regular menstruation but no galactorrhoea (group B). Both groups showed equivalent increases in prolactin levels after stimulation with 200 micrograms thyrotrophin-releasing hormone (TRH) during the follicular and luteal phases of the menstrual cycle. Patients in group A had a greater increase in luteinizing hormone levels after 100 micrograms i.v. injection of a luteinizing hormone-releasing hormone during the follicular phase (P less than 0.05). Following a 60 mg oral dose of buspirone hydrochloride on day 22 of the menstrual cycle, patients in group A had a greater increase in prolactin levels than patients in group B (P less than 0.01). This reflects hyper-responsive 5-hydroxytryptamine type 1A (5HT1A) receptors in group A patients and may explain the presence of galactorrhoea in these patients despite normal basal and post-TRH prolactin levels.