Some depressed patients may suffer from restricted central
hypothyroidism, which could occur if levels of the thyroid hormone
transport protein transthyretin were low. CSF transthyretin was measured in
eight inpatients with refractory major depression and nine neurological
patients. The depressed patients had significantly lower transthyretin
levels than the comparison subjects, suggesting that central
hypothyroidism, with normal peripheral thyroid concentrations, could occur
in some depressed patients.