[Determining the thyroid hormones T3 and T4 in the urine: an unreliable test for hypothyroidism]

A 24-year-old woman complained of tiredness, sensitivity to cold, and feelings of depression. A diagnosis of hypothyroidism based on decreased 24 h urinary T3 and T4 excretion was made, and she was treated with levothyroxin. No blood tests were done. She was referred with the question if she had other endocrine disorders. Her periods were regular, and on physical examination no abnormalities except slight acne were found. Similarly, hypothyroidism was diagnosed by decreased thyroid hormone excretion in 24 h urine, again without blood tests, in a 68-year-old woman whose mother had a goitre, and who had already been prescribed liothyronine. She had no complaints, and physical examination was unremarkable. The thyroid gland was not palpable. Thyroid peroxidase antibodies were absent in both patients. After discontinuation of medication with thyroid hormones they both remained euthyroid. It is concluded that thyroid disease did not exist in those 2 patients. Measurement of 24 h urinary T3 and T4 excretion is not an accurate diagnostic test for hypothyroidism.