Baseline thyroid hormones in depressed and non-depressed pre- and early-pubertal boys and girls

Objective: To examine baseline thyroid hormones in a large group of well-characterized pre-and early-pubertal boys and girls who met criteria for major depressive disorder (MDD) and a comparison group of normal children without psychiatric disorders. Methods: 45 children with MDD (10.6 years ± 1.4 year) and 56 healthy controls (10.0 ± 1.7 year) who participated in a large, psychobiologic protocol are included in this report. As part of the screening for eligibility, baseline samples were drawn for thyroxine (T4), triiodothyronine (T3) uptake, and thyroid stimulating hormone (TSH). Free thyroxine index (FTI) also was computed. Results: Between-group analyses were carried out controlling for various demographic variables significantly related to thyroid hormones [e.g. age, gender, body mass index (BMI) and their interactions]. For many hormones there were significant effects for age and gender. For T4, MDD boys had lower T4 compared with boys in the normal group. No differences were noted between MDD girls and normal girls. For TSH, MDD boys had lower concentrations compared with normal boys while no differences were noted in girls. For T3 uptake, the MDD group had lower uptake compared with the normal group. For FTI, there were no group differences. Similar to most studies of adults with depression, all our subjects were euthyroid. Unlike the adult studies, we found lower T4 concentrations in the MDD group rather than higher. Group differences in thyroid hormones were noted primarily in boys. The large sample size of this study allowed for the control of multiple variables, which has not been done in past studies. Without such controls, true findings may be masked in other studies of depression. Thus, our findings suggest the possibility of developmental differences in the relation of thyroid hormone and depression.