Plurihormone secreting pituitary macroadenoma masquerading as thyrotoxicosis: Clinical presentation and diagnostic challenges

Thyroid stimulating hormone (TSH) secreting adenomas are the rarest type of pituitary adenomas (1:1 in the population; 0.2- 2.8% of adenomas). Plurihormonal thyrotropic adenomas are even rarer usually having cosecretion of growth hormone (GH) and prolactin. We report perhaps for the first time, TSH, GH, adrenocorticotrophic hormone (ACTH) and gonadotropins secreting pituitary macroadenoma diagnosed in a 40 year lady presenting with features of thyrotoxicosis for 5 months, amenorrhea for 3 months and newly diagnosed diabetes and hypertension for 2 months along with headache, nausea, and vomiting, who had acromegaloid habitus, grade-II goitre, increased uptake on Technitium-99 pertechnate thyroid scan (4.1%; normal: 0.24-3.34%), with increased T3 (5.98 pg/ ml; 1.5-4.1), increased T4 (2.34 ng/dl; 0.9-1.8), inappropriately high TSH (2.32 μIU/ml; 0.4-4.2), insulin like growth factor-1 (711 ng/ ml; 109-264), non-suppressed post-glucose GH (15.9 ng/ml; <1 ng/ml), normal estradiol (52 pg/ml; 21-251), inappropriately high luteinizing hormone (53.5 mIU/ml; 1.1-11.6), inappropriately high follicle stimulating hormone (59 mIU/ml; 3-14.4), non-suppressed overnight dexamethasone cortisol (5.8 mcg/dl; <2), elevated ACTH (58 pg/ml 5-15), withdrawal bleed on progestrogen challenge, bitemporal hemianopia on automated perimetry and pituitary macroadenoma on MRI imaging of sella. Thyroid hormone resistance was ruled out by documenting normal sex hormone binding globulin and ferritin levels. Her clinical and biochemical phenotype was not suggestive of multiple hormone resistance seen in pseudohypoparathyroidism. This report intends to highlight the challenges in the diagnosis of plurihormonal thyrotropic adenoma.