Endocrine Abstracts

Introduction: Hypogonadism is known to persist after treatment of hyperprolactinemia, necessitating androgen therapy in young male patients. Aromatisation of testosterone to estradiol can result in tumor expansion. We report a patient with persistent hypogonadism post treatment of macroprolactinoma and discuss challenges involved in the management.

Case report: A 51-year-old gentleman was admitted for streptococcal meningitis. Brain imaging revealed a pituitary macroadenoma with invasion into the cavernous sinus and erosion into the sphenoid sinus resulting in persistent cerebrospinal fluid (CSF) rhinorrhea. Laboratory investigations: FSH <1 IU/l (RI 1–19), LH <1 IU/l (RI: 1–19), Total Testosterone <1 nmol/l (RI: 5–30), free T₄ 14 pmol/l (RI: 8–21), TSH 0.51 mIU/l (RI: 0.34–5.6), Prolactin 12 867 mIU/l (RI: 77–274), Short synacthen test response (293à848à977 nmol/l). He underwent transphenoidal removal of the prolactinoma and post operatively was complicated by panhypopituitarism requiring thyroxine and hydrocortisone replacement. A weekly dose of 2.5 mg of Cabergoline was needed to normalise prolactin levels. He reported low mood, libido and erectile dysfunction post surgery. FSH, LH and testosterone remained undetectable. He was started on i.m. testosterone at 100 mg every 4 weeks with normalisation of testosterone levels to 26 nmol/l and resolution of hypogonadal symptoms. His prolactin levels, expectedly, increased to 343 mIU/l. There were no signs and symptoms of raised intracranial pressure or cavernous sinus syndrome.

Discussion: Hyperprolactinemia suppresses the pulsatile secretion of GnRH resulting in hypogonadism. Estrogen, from aromatisation of testosterone, stimulates prolactin secretion by stimulating prolactin gene transcription and disrupting the inhibitory influence of dopamine. We discuss benefits and problems of various management options should there be tumor expansion post initiation of testosterone. These include increasing the dose of cabergoline or the addition of an aromatase inhibitor. Regular prolactin measurements and imaging of the pituitary are needed.