(13.06) Title: Disproportionate Hyperprolactinemia in a Patient with ESRD and Functioning Pituitary Adenoma

Prolactin, an anterior pituitary hormone secreted by lactotrophs. Prolactinomas are most common pituitary adenomas and show a 10:1 female-to-male incidence ratio.Types include microadenomas (< 1cm), macroadenomas (1-4 cm), and giant adenomas ( >4 cm). Studies show correlation between adenoma size and hyperprolactinemia, with microadenomas (< 200 ng/mL), macroadenomas (200-1000 ng/mL), and giant adenomas ( >1000 ng/mL). Hyperprolactinemia is common in ESRD patients, with highest reported level up to 600 ng/ml. We present a case of macroadenoma in ESRD patient having disproportionate hyperprolactinemia.

Case(s) Description :

52-year male with diabetes, hypertension, ESRD presented with worsening frontal headaches, blurred vision, and intense left eye pressure for 4 months. CT brain showed pituitary soft tissue enlargement and osseous remodeling of skull base. He denied decreased libido, hand/foot/tongue growth, coarsening of facial features, galactorrhoea, ring/shoe size alteration. Lab showed prolactin ( >4700 ng/ml), LH (20.2 mIU/ml), FSH (18.4 mIU/ml). MRI revealed 2.0 x 3.1 cm pituitary macroadenoma with delayed enhancement, bony remodeling, and sellar floor extension into sphenoid portion of clivus, displacing left cavernous (ICA) leftward and pituitary gland and stalk rightward. Based on tumor function, neuro-surgical intervention was ruled out. Further evaluation showed non-proliferative retinopathy, macular edema with no signs of bilateral hemianopsia. He was started on cabergoline 0.5 mg biweekly. After 6 weeks of treatment, prolactin levels were decreased to 441 ng/ml, with symptom improvement and hormonal stabilization.

Discussion :

Hyperprolactinemia is caused by pituitary adenomas, hypothalamic tumors, medications, and hypothyroidism. Prolactinomas make up more than half of pituitary adenomas. Usually benign, they present with symptoms due to mass effects including headaches, visual field defects, infertility, gynecomastia, low libido, and erectile dysfunction. Our case describes a macroadenoma of 2.0 x 3.1 cm with prolactin levels >4700 ng/mL in ESRD patient. Hyperprolactinemia is seen in 25-57% men and 73-91% women with ESRD on dialysis. Possible hypothesis for marked hyperprolactinemia seen in our patient is combination of reduced prolactin clearance due to ESRD, increased secretion, and stalk effect with compression of pituitary stalk containing tubero-infundibular pathway disrupting dopamine inhibition. Functioning adenomas produce prolactin and respond to medical management, as seen in our case. First-line treatments for symptomatic and functional prolactinomas include dopamine agonists for tumor shrinkage and to reduce prolactin levels, leading to reversal of symptoms from mass effect and hypogonadism. Surgery is considered for refractory adenomas. Prolactin levels and MRI 6-12 months after starting treatment are used to guide the tapering of treatment versus decision for surgery.

Prolactin levels are disproportionately high relative to the size of tumor in ESRD patients and exact mechanism is unknown. It has not been reported in the medical literature, so further research is required.