A 23-year-old woman began oral contraceptive pills 6 weeks ago. She reports palpitations and mild heat intolerance but denies weight loss or neck pain. Vital signs show HR 92 bpm, BP 118/76 mmHg, RR 16/min, temperature 37.2°C. Laboratory studies reveal total T4 11.2 ng/dL (normal 4.5-12), free T4 1.2 ng/dL (normal), and TSH 1.8 mIU/L (normal). Thyroid ultrasound shows no nodules. Which mechanism best explains these findings?
- A)Primary thyroid gland hyperplasia
- B)Reduced hypothalamic TRH secretion
- C)Decreased activity of type 1 deiodinase
- D)Increased production of thyroxine binding globulinGABARITO
- E)Resistance of peripheral tissues to thyroid hormone
Explicação
Estrogen increases hepatic synthesis of thyroxine binding globulin. More circulating T4 becomes protein bound, so total T4 rises while free T4 and TSH remain normal because the patient is euthyroid. This is a classic laboratory change rather than true hyperthy... Ver explicação completa e trilha adaptativa →