Driving Through Fatigue

A 48-year-old school bus driver presents with fatigue, cold intolerance, weight gain, constipation, dry skin, and hair loss over 4 months, with her last menstrual period 5 months ago. She has a history of hypothyroidism, previously managed with levothyroxine, but has been inconsistent with medication adherence. Her family history includes autoimmune thyroid disease. Examination reveals dry skin, thinning hair, loss of eyebrow hair, and non-pitting edema, with normal cardiac and neurologic findings aside from mildly delayed deep tendon reflexes. Lab results show

Total cholesterol                                                               6.7 mmol/L (3.5–5.2)

Thyroid-stimulating hormone (TSH)                           185 mIU/L (0.34–5.60)

Free thyroxine (FT4)                                                           2.3 pmol/L (7.0–17.0)

Anti–thyroid peroxidase (TPO) antibody titer                       Very high

Human chorionic gonadotropin (β-hCG), serum                  Negative

Prolactin                                                                                           10 µg/L (3–27)