(100) Falsely Elevated Prolactin Level in a non-Pregnant Female secondary to Physical Exercise - Case Report and Discussion

Aim

Hyperprolactinemia occurs when the human prolactin level (PRL) is elevated (above 25 ng/mL in women) and can arise from many etiologies, including drugs, tumors, exercise, physiologic changes and stress, and/or psychological stress. Hyperprolactinemia occurs in < 1% in the general population and is estimated to have a mean prevalence of 30 cases per 10,000 women. PRL is a hormone secreted by lactotrophs of the anterior pituitary. Its secretion is primarily regulated via inhibition by dopamine, though PRL secretion can also be inhibited by γ-aminobutyric acid (GABA) release. PRL secretion can be stimulated by increases in thyroid releasing hormone (TRH) and/or estrogen³. Elevated PRL levels secondary to exercise can persist for up to 24 hours.

Methods

Case report - institutional review board (IRB) exempt.

Results

This patient is a 28 year old female G0 being evaluated for infertility and bilateral galactorrhea. The patient denies menstrual irregularities, loss of libido, headache or changes in vision.

Upon evaluation of relevant labs, she was found to have a normal FSH (3.0), LH (6.5), TSH (2.26), estradiol of 265, Hgb 13.3 and normal LFT. Her prolactin was found to be elevated at 46.5, however, repeat testing was normal 21.3 a month later.

Conclusion

Transient elevation of prolactin levels can be due to a physiologic elevation or physical exercise.

Other causes of this presentation may include pregnancy, breast feeding, hypothyroidism prolactinoma, antipsychotic-induced hyperprolactinemia caused by first and second-generation antipsychotics (risperidone) due to their blockage of dopamine, a hormone that inhibits release of prolactin from the pituitary gland, or prolactinoma, a benign tumor of the pituitary gland. Considering this patient was not on any such medications and did not have concern for a hormone-producing lesion (i.e vision problems), these differentials may be ruled out as causes for her elevated prolactin level.

A common practice is to inform the patient that a breast exam cannot be performed before checking prolactin levels, as nipple stimulation can temporarily increase this measurement.

On further questioning, the patient had an intensive workout at the gym before checking prolactin levels, potentially leading to higher than normal values as a result of stress and physical stimulation. The patient had an unremarkable pregnancy a year later.