Hypothyroidism: The Daily PANCE Blueprint
A 46-year-old woman presents with 4 months of fatigue, a 5-kg weight gain, constipation, and feeling cold when others are comfortable. Her menstrual periods have become heavier. On examination, her skin is dry, her heart rate is 56/min, her thyroid gland is diffusely enlarged, firm, and nontender, and the relaxation phase of her ankle reflexes is delayed. She takes no medications, has never had neck surgery or radiation, and has no headaches or visual changes. Which laboratory result is most consistent with this presentation?
A. Low TSH, low free T4
B. Elevated TSH, low free T4
C. Low TSH, elevated free T4
D. Elevated TSH, elevated free T4
E. Normal TSH, normal free T4
Answer and topic summary
The answer is B. Elevated TSH, low free T4
This is overt primary hypothyroidism, and in iodine-sufficient countries the usual cause is Hashimoto (chronic autoimmune) thyroiditis, which fits her firm, nontender goiter. When the thyroid gland itself fails, free T4 falls and the pituitary responds with a rising TSH, so the pattern is elevated TSH with low free T4. TSH is the best initial screening test; an elevated TSH with a normal free T4 is subclinical hypothyroidism, and anti-TPO antibodies support a Hashimoto cause. A low or inappropriately normal TSH with a low free T4 points to central (pituitary or hypothalamic) hypothyroidism, which does not cause a goiter and usually comes with other pituitary clues. Low TSH with high free T4 is hyperthyroidism, and a high TSH with high free T4 suggests a TSH-secreting adenoma or thyroid hormone resistance. Treatment is daily levothyroxine, titrated to the TSH every 6–8 weeks.
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