Hormones and Depression
By grading the severity of symptoms of depression, scientists are able to measure the hormonal correlates of depression and as a consequence the effect of hormonal treatments. Several hormones have been identified to be associated with depression.
- Thyroid hormones
Thyrothropin releasing hormone (TRH) is a hormone that stimulates the release of thyroid stimulating hormone (TSH). This, in turn stimulates the production of thyroid gland hormones T3 and T4, which have an important role in metabolic processes. In depressive patients treated with TRH, the symptoms of the depression were strongly reduced. They show a lower thyroid response to TSH in comparison with non-depressive patients. Recent studies have shown that people suffering from depression often have a lot of antibodies against the thyroid gland and a high concentration of TRH in the cerebrospinal fluid.
- Growth hormone and prolactin
Despite the normal concentrations af growth hormone (GH) in depressive patients, they often exhibit disadvantageous responses to, for example, insulin induced hypoglycemia (a low glucose concentration in the blood) and serotonin stimulation. TRH also indices an abnormal increase in depressive people.
Another thing noticed in depressive patients, is a heightened prolactin concentration. Despite contradictory results of correlative studies between GH and prolactin, it is obvious that there is a fundamental difference between the endocrine function of depressed and non-depressed individuals. This suggests that there are differences in physiological mechanisms that are at the base of their endocrine feedback control systems.
Excessive cortisole production is often perceived in depressed people. The negative feedback system of the hypothalamic-pituitary-adrenal axis (HPA) seems to be functioning poorly, possible because of a reduction of corticosteroid receptors in the brain. This also appears clearly in the dexamethasone suppression test. Dexamethasone is an artificial steroid that mimics cortisol. When this is administered at midnight, a suppression of the cortisol concentration is expected through the negative feedback system. This suppression is not noticed in depressive patients. Cortisol is also called the stress hormone because it is released under any form of stress. Strangely, depressive individuals show a reversed diurnal rhythm where the cortisol concentrations are higher at night than during the day.
A lack of estrogen is also associated with depression. Decreases in estrogen values occur, for example, after quitting birth control or in the postnatal period of the mother. This could lead to what is called postnatal depression.
Yet, recent research suggests that there might be other causes than the endocrine changes. The many social factors that occur after the birth of a baby, can also play an important part in the development of a postnatal depression. One of the reasons behind this idea is the fact that men have an almost equal chance of developing postnatal depression. And since the hormone concentrations are very different between men and women, this suggests that endocrine changes might not be the primary cause of postnatal depression.