Mary, a 32-year-old woman, presents to the endocrinology clinic with complaints of chronic fatigue, cold intolerance, weight gain, and irregular menstrual cycles. She also reports difficulty breastfeeding after the birth of her last child three years ago, despite being able to breastfeed her first child without issues. She has noticed thinning of her pubic and axillary hair and decreased libido. Her history reveals that her last delivery was complicated by severe postpartum hemorrhage requiring blood transfusions. She has not received regular medical follow-ups since then. Physical Examination: •Pale skin and thinning of axillary and pubic hair. •Her temperature is 99 °F, heart rate is 62 beats/min, blood pressure is 98/68 mm Hg, respirations are 19 breaths/min, and oxygen saturation is 97% on room air. •No palpable goiter. •Generalized fatigue and lethargy without focal neurological deficits. Diagnostic Workup: 1.Laboratory Results: Test Result Reference TSH 0.1 µg/mL 0.4 – 4.0 µg/mL Free T₄ 0.3 ng/dL 0.9 – 1.7 ng/dL Cortisol 0800h: 2 µg/dL 0800 h: 5-23 µg/dL//1600 h:3-15 µg/dL; 2000 h: <50% of 0800 h Follicle-stimulating hormone 2 mIU/mL Male: 4 - 25 mIU/mL Female: premenopause 4-30 mIU/mL; midcycle peak 10-90 mIU/mL; postmenopause 40 - 250 mIU/mL Luteinizing hormone 1 mIU/mL Male: 6 - 23 mIU/mL Female: follicular phase 5 - 30 mIU/mL midcycle 75 - 150 mIU/ml postmenopausal 30 - 200 mIU/mL Prolactin (hPRL) 6 ng/mL Male: <17 ng/mL Female: <25 ng/mL Sodium (Na⁺) 136 mEq/L 136 - 146 mEq/L ACTH 2 pg/mL 0800 hr: 10-60 pg/mL Estradiol 4 pg/mL 20-200 pg/mL 2.Imaging: MRI of the pituitary shows an empty sella. What is the first hormone deficiency that should be addressed in the treatment of this disorder?
