The effect of the menopause on prolactin levels in patients with hyperprolactinaemia

Microprolactinomas have been reported to resolve spontaneously after pregnancy and there have been suggestions that oestrogen therapy increases the size of microprolactinomas. Little is known, however, about the effect of the menopause in patients previously known to be hyperprolactinaemic. The aim of this study was to find out if pregnancy or the menopause leads to an alteration in prolactin levels.

We conducted a retrospective study of 148 case notes of patients with hyperprolactinaemia and microprolactinomas treated at the Radcliffe Infirmary during the period 1976-96. Sixty-nine female patients who had not had pituitary surgery as treatment for microprolactinoma were used as a control group. None of this group became pregnant or reached the menopause. They were compared with 25 female patients who became pregnant, 11 who became menopausal and 11 who were male. Subjects were excluded from the analysis if there were no follow-up data off dopamine agonist treatment or if they were surgically cured. Data were gathered on demographic parameters, treatment given, scan abnormalities, prolactin levels at diagnosis and last follow up, prolactin levels pre- and postpregnancy as well as pre- and postmenopause. The pregnancy, postmenopausal and male patient groups were compared with the control group and each other to see if they had a higher frequency of normalization of their prolactin levels during follow up. Various factors were examined as possible variables for the normalization of prolactin, including the detection of scan abnormalities at diagnosis, prolactin levels at diagnosis as well as treatment with dopamine agonists and duration of follow up.

Forty-five percent of the menopausal group, 24% of the pregnancy group and 18% of the male group subsequently normalized their prolactin levels during the period of the study in comparison with 7% of the control group. The menopausal groups had a significantly higher chance of normalizing their prolactin compared to the control group (P < 0.005), whilst the pregnancy group showed a non-significant trend towards normalizing their prolactin (P = 0.06). The detection of scan abnormalities, treatment with dopamine agonist therapy and duration of follow up were not associated with normalization of prolactin levels.

Female patients with hyperprolactinaemia who pass through the menopause have a significant chance of normalizing their prolactin levels. Females who pass through pregnancy may have a higher chance of normalizing their prolactin levels. The menopause is an indication for reassessment of the need to continue to treat hyperprolactinaemia and microprolactinoma.