Cardiac Tamponade, Pituitary Hyperplasia, and Macroorchidism in Severe Primary Hypothyroidism.

This case reports a rare and complex presentation of severe primary hypothyroidism (PH) in an 18-year-old male. The patient presented to the emergency department with dyspnea due to impending cardiac tamponade, requiring emergency pericardiocentesis. Further evaluation revealed features of long-standing PH, including short stature, cognitive delay, and pubertal discordance with macroorchidism. Laboratory tests showed extreme elevation of TSH and multiple anterior pituitary hormone deficiencies. Magnetic resonance imaging (MRI) revealed a large sellar mass mimicking a pituitary adenoma. Treatment was initiated with levothyroxine and physiological hydrocortisone. Follow-up at 6 months showed improvement in clinical status and TSH level and significant regression of the pituitary mass on repeat MRI, confirming the diagnosis of pituitary hyperplasia in primary hypothyroidism (PHPH). This case highlights the potential for severe, life-threatening manifestations of PH and emphasizes that a therapeutic trial with levothyroxine is the definitive approach to differentiate PHPH from a TSH-secreting pituitary adenoma, thus avoiding unnecessary surgical intervention.