Endocrine Abstracts

Introduction: Prolactin is involved in lactation and reproduction. Endocrinologists should be familiar with physiological effects of prolactin in women, particular in key moments: breastfeeding and menopause. We aimed to report two females with unusual prolactin-related challenges: the first case corresponds to a postpartum woman with normoprolactinemia and breastfeeding problems; the second case concerns a menopausal woman with a prolactinoma who developed hot flashes following normalization of prolactin levels.

Clinical cases: A 32 year-old woman was referenced 2 months after delivery of her first child, after evaluation by a Lactation consultant. She sought help for not being able to exclusively breastfeed since the birth, with no let-down reflex/draught. She had two normal serum prolactin measurements (14.3 and 8.3ng/ml, normal range <25). Her baseline pituitary function was normal. She was advised to breastfeed on full-demand, mainly at night, to increase her lactation function. A 50 year-old woman was diagnosed with a macroprolactinoma after complaining of headache, although she had a secondary amenorrhea since 26 years-old-not previously investigated. At diagnosis, she had elevated prolactin levels at 2500ng/ml, and low LH and FSH levels at 0.36 and 5.26 mUI/ml, respectively; remaining pituitary function was normal. Pituitary MRI showed a 3.6 cm-cystic pituitary mass with cavernous sinus invasion compressing the optic chiasm. She initiated cabergoline, with good biochemical and structural response. Within 6 months on cabergoline, prolactin levels normalized, with a concomitant increase of LH/FSH levels up to the range for a postmenopausal woman, respectively 19.27 and 34.31 mUI/ml. At this point in time, the patient started to report menopause-like symptoms, particularly hot flashes, which she never experienced before, even when she became amenorrheic.

Conclusion: Despite the fact that lactation is a well-known cause of secondary hyperprolactinemia, normal prolactin levels can be found in breastfeeding women. Since delivery and during breastfeeding, serum prolactin levels may slowly decline over time; also serum prolactin peaks throughout the day in breastfeeding women, and correlate with moments of suckling stimulation. With the second case, we learned that hyperprolactinemia contributed to abolishment of menopause-related hot flashes, due to gonadotropin/GnRH suppression. Although hot flashes in menopausal women are classically attributed to estrogen deficiency, this case suggested that elevated FSH/lH may also play a role. This may be due to proximity of hypothalamic GnRH neurons with thermoregulatory neurons, explaining a possible association of pulsatile LH-release and occurrence of hot flashes.