Case History/Examination:
A 37-year-old male presented to the clinic with palpitations, weight loss, and easy fatigability. On examination, he appeared thin, with a BMI of 19 kg/m², and exhibited resting tachycardia with a regular pulse of 104 bpm. He had tremors in his outstretched hands and bilateral neck swelling with an audible thyroid bruit. There were no eye signs of hyperthyroidism or evidence of pretibial myxedema. He had been treated for thyrotoxicosis over the past seven years outside the hospital, receiving anti-thyroid medications and radioactive iodine (RAI) therapy. After RAI, he was started on levothyroxine. Despite gradually increasing the levothyroxine to the maximum dose, his TSH levels remained elevated, and symptoms of hyperthyroidism persisted. Initial workup showed a TSH of 48 µIU/mL (normal range: 0.35–5.5 µIU/mL), FT4 of 4.8 ng/dL (normal range for adults >20 years: 0.89–1.76 ng/dL), and FT3 exceeding 20 pg/mL (normal range: 2.4–4.2 pg/mL). The elevated FT4 and FT3 levels, alongside non-suppressed TSH, suggested a central cause of hyperthyroidism. The rest of the pituitary hormones were in the normal range except for raised testosterone with inappropriately average values of LH and FSH (Table 7)
Brain MRI revealed a 9 x 12 mm mass in the sellar region