Twenty Four-Hour Prolactin Profiles and Prolactin Responses to Dopamine in Long Distance Running Women*

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Abstract
Long distance women runners have a high incidence of oligoamenorrhea. In order to study the possible role of PRL in contributing to their menstrual dysfunction, we evaluated PRL secretion in eumenorrheic (n = 7) and oligomenorrheic runners (n = 9) who averaged 25-50 miles/week, as well as nonrunning women (n = 5) during the midfollicular phase of their cycles. Serum estradiol, progesterone, testosterone, FSH, LH, TSH, and T4 were similar among the three groups. The mean 24-h ± SE PRL concentrations between the three groups: nonrunners, 12.9 ± 0.6 ng/ml; eumenorrheic runners, 13.5 ± 0.4 ng/ml; and oligomenorrheic runners, 15.0 ± 0.8 ng/ml, were not significantly different. A dopamine (DA) infusion, 0.004 μg/kgmin, produced physiologic serum DA levels in these subjects. The nadir of serum PRL levels during DA infusion was similar in each group, which argues against an abnormality in dopaminergic tone in the runners with menstrual dysfunction. Our findings of normal 24-h PRL secretion and appropriate PRL responses to DA in women runners with menstrual dysfunction do not support a role for PRL in this disorder.