A cannulated prolactin series reduces the need for further investigations in women with infertility and lowers the number of false positive screening prolactin measurements

Background: The prevalence of hyperprolactinaemia in women presenting for infertility investigation has been found to be up to 17%, and many of these women are asymptomatic. Prolactin levels may be elevated by stress, including phlebotomy and not be of clinical significance. A cannulated prolactin study may be a useful way to discriminate this.

Aim: To determine the utility of a cannulated prolactin series in women presenting with infertility who have a raised prolactin measurement at referral for first fertility consultation.

Materials and methods: All women referred to two fertility centres had a prolactin level measured prior to first appointment over a two-year period. If the level remained elevated on the second measure after macroprolactin precipitation, women were referred for a cannulated prolactin series. If the prolactin concentration fell within the reference range during the series then the result was regarded as normal.

Results: Forty-four (2.7%) of 1660 women seen for a first specialist appointment had persistently raised prolactin concentrations after two samples and were referred for a cannulated series. The proportion of women whose prolactin was found to be normal during the cannulated prolactin series was 61% (95% CI 47-74%). Even in patients with a referral prolactin of greater than 1000 mU/L, 45% had a normal two-hour cannulated series.

Conclusion: A high proportion (61%) of women with raised prolactin at time of referral for first specialist appointment had a normal prolactin after a two-hour cannulated series. A cannulated prolactin study can avoid unnecessary further investigations in these women.