Case Report: Reversible central hypothyroidism-like thyroid dysfunction revealing ACTH-independent cushing syndrome during pregnancy

The article describes a case of a 29-year-old woman at 17 weeks of gestation with low free thyroxine (FT4 9.18 pmol/L) and normal thyroid-stimulating hormone (TSH 0.5 μIU/mL) despite levothyroxine treatment at 75 μg daily. This unusual combination suggested central hypothyroidism rather than primary hypothyroidism. Clinical examination revealed rapid weight gain, moon face, buffalo hump, and purple abdominal striae. Laboratory tests showed loss of cortisol diurnal rhythm, markedly elevated 24-hour urinary free cortisol, and suppressed ACTH. MRI identified a right adrenal mass. ACTH-independent Cushing syndrome caused by an adrenal adenoma was diagnosed. The patient underwent retroperitoneal laparoscopic adrenalectomy at 18 weeks and 3 days of gestation. After surgery, FT3, FT4, and TSH levels normalized and levothyroxine was gradually discontinued without recurrence of hypothyroidism. The patient delivered a healthy girl at 39 weeks of gestation.