Thyrotropin, but not a polymorphism in type II deiodinase, predicts response to paroxetine in major depression

Abstract

The determinants of response to antidepressant treatment in major depression are unknown at present. The aim of the present study was to establish whether response is predicted by Hypothalamus-Pituitary-Thyroid (HPT) axis parameters or by a recently discovered polymorphism in the enzyme type II deiodinase (DII), which catalyzes the production of T3 in the brain. We analyzed prediction of response to paroxetine treatment by calculating response rates per tertile of HPT-axis parameters and per DII genotype. Ninety-eight outpatients with major depression (DSM-IV) were included. Serum concentrations of TSH, FT4 and delta TSH in a DEX/CRH-TRH test were measured. In addition, the presence of a polymorphism in the DII sequence (Thr92Ala) was determined. The overall treatment response was 48 of 98 patients (49%). After exclusion of patients with subclinical hypothyroidism and/or TPO antibodies (n = 16), higher serum TSH significantly predicted response (response rate per tertile from low to high TSH: 36%, 42%, and 67%). Heterozygous patients for the DII polymorphism (44%) had slightly lower serum TSH (P = 0.03) as compared to patients with the wild-type DII (47%). The polymorphism was unrelated to treatment response. Higher serum TSH was associated with response to paroxetine in patients with major depression.