Endocrine Abstracts

JOINT2528

Introduction: Hyperprolactinemia is a common finding in patients on antipsychotic medications. Markedly elevated prolactin levels warrant further investigation.

Case Presentation: A 57-year-old woman with schizophrenia on risperidone was referred to the endocrinology clinic after routine testing revealed asymptomatic hyperprolactinemia. She had no headaches, or visual disturbance and was 2-years post-menopause. Her main concern was a 3-year history of progressive large volume, watery diarrhoea associated with 12kg weight loss and a hyperpigmented rash. She denied flushing, wheezing, or symptoms of hypoglycaemia. She had been previously investigated with a normal colonoscopy and been diagnosed with irritable bowel syndrome. She had type 2 diabetes and had no family history of endocrinopathy. On examination, she had no clinical endocrinopathy. Skin examination revealed well-demarcated, hyperpigmented macules over her gluteal, inner thigh, feet and inframammary regions. The remainder of her clinical examination was normal, including normal visual acuity, eye movements and visual fields to confrontation with a red pin. Laboratory investigations showed a significantly elevated prolactin of 39,393 mU/l(normal range <496 mU/l)with suppressed gonadotropins. The remainder of her anterior pituitary function and calcium were normal. The prolactin level was too high to be attributed to antipsychotic therapy. Pituitary MRI confirmed a 22 mm macroadenoma with right cavernous sinus invasion but no optic chiasm compression. After psychiatric consultation, risperidone was switched to aripiprazole, leading to an improvement in prolactin levels (9,315 mU/L). Further workup for her diarrhoea and rash revealed elevated 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA) and chromogranins A and B, with normal fasting gut peptides and glucagon. Imaging, including 68Ga-DOTATATE PET-CT and triple-phase CT, identified a primary ileal neuro-endocrine tumour (NET) with mesenteric, liver, and lung metastases. Echocardiography showed no evidence of carcinoid heart disease and genetic testing for multiple endocrine neoplasia type 1 (MEN1) was negative. Histology confirmed a Grade 1 NET (Ki67 <3%). She was initiated on 4 weekly Lanreotide injections and vitamin B complex, resulting in a significant reduction in diarrhoea and resolution of her rash, with normalisation of 24-hour urine 5HIAA. Learning Points 1. While drug-induced hyperprolactinemia is common, significantly elevated prolactin levels necessitate further evaluation to exclude pituitary adenomas. 2. Aripiprazole is an atypical antipsychotic, which is effective at reducing serum prolactin and pituitary adenoma size when dopamine agonist therapy is contra-indicated. This is an off-license use. 3. The combination of diarrhoea and a rash should alert the physician to the possibility of an underlying neuro-endocrine tumour.