A patient with low free T4 and low thyroid-stimulating hormone without hypopituitarism

A 39-year-old entertainer was referred in November 2000 for suspected secondary hypothroidism found during a routine insurance check. Thyroid stimulating hormone (TSH) was 0.30 mIU/L (NR 0.47-4.68 mIU/L) and total T4 was 21.6 nmol/l (NR 57.9-154.4 nmol/l). She had enjoyed good past health and gave birth to a baby girl at 32 weeks gestation in July 2000. She was clinically euthyroid and there was no goiter. Menses was regular with oral contraception. Thyroid function was rechecked with free T4 7.9 pmol/l (NR 10.2-19.6 pmol/l) and TSH 5.44 mIU/l (NR 0.3-4 mIU/l). Further inquiry revealed that she had been taking a weight reducing drug since December 1999 for fear of potential weight gain during pregnancy. This was identified to be Tri-iodothyroacetic acid (Triac). Serial thyroid function tests showed gradual recovery of thyroid function after Triac was stopped.