Longitudinal studies of thyroid function during a four-week comparative trial of imipramine hydrochloride and L-tryptophan in 30 depressed patients showed a significant fall in the free thyroxine index during the first week of the trial, but otherwise measures of thyroid activity were within normal limits and showed no change during clinical recovery. Administration of 25µg of L-triiodothyronine (T3, liothyronine sodium) for 14 days was sufficient to cause some suppression of endogenous thyroid function and demonstrated that the pituitary-thyroid axis remains responsive during depressive illness. Ankle reflex time estimated prior to treatment was very significantly correlated with response to imipramine therapy, ie, the patients with faster ankle reflex times showed a greater improvement than those with a slower ankle reflex time. A similar correlation was found between a low serum cholesterol level and a good clinical response to imipramine treatment.
Whybrow PC, Coppen A, Prange AJ, Noguera R, Bailey JE. Thyroid Function and the Response to Liothyronine in Depression. Arch Gen Psychiatry. 1972;26(3):242-245. doi:10.1001/archpsyc.1972.01750210050010