Free-thyroxine index in psychotic and neurotic depression

Effects of thyroid hormones on central nervous system in aging

Support for the many relationships between thyroid hormones and brain function comes from both laboratory and clinical studies. Studies in laboratory animals provide convincing evidence for a neuroregulatory role of thyroid hormones in the brain, suggesting that they may affect behavior. This notion is supported by human studies which have revealed that the effects of thyroid hormones on brain function are most important during the development and maturation of the brain; thereafter, age does not seem to critically affect brain-thyroid hormone relationships.

Neuroendocrine aspects of primary endogenous depression--IV. Pituitary-thyroid axis activity in patients and matched control subjects

In order to ascertain the extent of hypothalamo--pituitary--thyroid (HPT) axis dysfunction in endogenous depression, we determined nocturnal serum thyrotropin (TSH) concentrations, TSH responses to thyrotropin releasing hormone (TRH) administration, and serum triiodothyronine (T3) and thyroxine (T4) concentrations in 40 Research Diagnostic Criteria primary, definite endogenous depressives and 40 individually matched normal control subjects. We also examined the relationships of the HPT measures to pre- and post-dexamethasone (DEX) serum and urine cortisol measures and, in the patients, to subject characteristics, the diagnosis of endogenous/melancholic depression by different systems, and the overall severity and specific dimensions of depressive symptomatology. Compared to their matched controls, the patients showed significant reductions in nocturnal serum TSH and serum T3 concentrations. Neither the TSH responses to TRH nor serum T4 concentrations were significantly different between the two groups of subjects. In the patients, none of the subject characteristics, diagnostic schemes for endogenous/melancholic depression or specific aspects of depressive symptomatology were significantly related to HPT activity. The measures of HPT activity were unrelated to measures of hypothalamo--pituitary--adrenal cortical (HPA) axis activity in both groups of subjects.

Endocrine changes and clinical profiles in depression: II. The thyrotropin-releasing hormone test

Thirty-one (43%) of 68 patients with primary depression were found to have a blunted thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH). Increased thyroid activity, as measured by the free thyroxine index (FTI), was present in 16 (24%) of the patients. Patients with blunted responses had a higher mean FTI level than those with normal responses. Patients with blunted responses were significantly more likely to exhibit the symptoms of depersonalization, derealization and agitation. There was no clear association between blunting and any particular diagnostic category of depression. Patients with blunted responses and high FTI values were more likely to report significant long-term environmental difficulties than patients with blunted responses and normal FTI values. It is suggested that there may be more than one mechanism responsible for blunting of the TSH response in depressed patients. In some patients blunting may be due to negative feedback from increased output of thyroid hormones, possibly released as part of a stress response. In other patients blunting may be due to a different mechanism, possibly involving pituitary gland dysfunction. These mechanisms would not necessarily be mutually exclusive in any one patient.

Thyroid function tests in thyroid and nonthyroid disease

Modern day evaluation of thyroid disorders requires a combination of accurate clinical judgement and reliable, sensitive, and specific thyroid functions tests. Principle among the latter are thyroxine (T4) 3, 5, 3'-triiodothyronine (T3), and thyroid-stimulating hormone (TSH). Also playing an important role in special situations are free thyroxine, an assessment of bound and unbound thyroid-binding globulin, TRH stimulation, long-acting thyroid stimulator (LATS), antibodies to thyroid hormone and to thyroid receptors. Basic to interpretation of these tests in the clinical setting is a comprehension of the relationship of the hypothalamus, the pituitary, and the thyroid gland as well as a knowledge of the peripheral metabolism of thyroxine and triiodothyronine. The role of each of these laboratory tests in the evaluation of hyper- and hypometabolic states, their alteration in nonthyroid and other endocrine disorders, and the effects of environmental and physiological factors on these tests are reviewed.

Neuroendocrine tests of monoamine function in man: a review of basic theory and its application to the study of depressive illness

Neuroendocrine tests are now available for studying monoamine function in the brains of patients with mental illness. Great care is required in the selection of drugs which act upon specific monoamine receptors to produce specific hormonal responses. Equal care is required in the control of biological variables which may influence hormonal release. Recently reported neuroendocrine studies of depressive illness are assessed in these terms. The results of these studies support the hypothesis that there is defective noradrenergic function in the brains of some patients with depressive illness.