THE PREVALENCE OF HYPERPROLACTINEMIA AND ASSOCIATION WITH MARKERS OF AUTOIMMUNE THYROID-DISEASE IN SURVIVORS OF THE WHICKHAM SURVEY COHORT

OBJECTIVE Few data exist on the prevalence of hyperprolactinaemia in t he community. This study was intended to determine the prevalence of h yperprolactinaemia in a sample closely matched to the current British population aged 38 years and over. DESIGN AND PATIENTS The 1877 surviv ors at the 20-year follow-up of the Whickham Survey were a cross-secti onal sample of the community aged 38 years and over. Serum was frozen and stored at -30 degrees C from 90% of the survivors(751 men, 924 wom en, median age 58 years (range 38 to 93 years)) who participated in th e follow-up survey. MEASUREMENTS Two years after the follow-up survey, serum prolactin concentrations were measured by ELISA/1 step sandwich assay (reference range less than or equal to 600 mU/I in men and wome n). A repeat prolactin measurement was made in those subjects who had prolactin levels within the top 2-5% of men and women in this sample. RESULTS At screening, 0.7% of the men and 2.5% of the women had serum prolactin levels greater than 600 mU/I. For men, 2.5% were above 400 m U/I. The prevalence of hyperprolactinaemia, if defined as greater than 400 mU/I in men and greater than 600 mU/I in women on repeat testing, was 1.4% in the men and 1.2% in the women. The aetiology in men was p rolactin-raising drugs (n=3), renal failure (n=1), microprolactinoma ( n=1), and unknown (n=2), and in women it was prolactin-raising drugs ( n=7), microprolactinoma (n=1), and unknown (n=1). Logarithmic transfor mation of serum prolactin concentrations produced Gaussian distributio ns with 95% reference ranges of 60-430 mU/I in men and 40-560 mU/I in women. No significant relationship was found in either sex between hyp erprolactinaemia and age or evidence of autoimmune thyroid disease at either survey. in women, there was no association with age, distance b eyond the menopause or duration of reproductive years but prolactin le vels were slightly higher in those on oestrogen therapy (geometric mea n prolactin 226 mU/I compared to 178 mU/I; t-test on log prolactin t=3 .79; P<0.0001). CONCLUSIONS This study has demonstrated that a gender- related reference range for serum prolactin is necessary. Pituitary pa thology is not common and screening with measurement of serum prolacti n is not warranted in middle-aged and elderly subjects. In asymptomati c subjects with modestly elevated serum prolactin levels (<3 SD above the mean), extensive pituitary imaging and investigation is unwarrante d. Autoimmune thyroid disease was not a significant cause of hyperprol actinaemia in this sample.