Clinical Aspects

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Most inferences concerning pineal hormones and diseases have come from studies with experimental animals. Thus, pinealectomy at an early time in development in some species can lead to premature ovarian function, and treatment with melatonin can suppress ovarian function. As described earlier, the amounts of melatonin secreted nocturnally decline just prior to and during pubescence. Moreover, an acute oral dose (1-3 mg/kg) given to young adults causes prolactin to be secreted. A number of different kinds of tumors can affect the function of the pineal gland, usually resulting in central nervous system disturbances and either premature or delayed gonadal functioning, especially when the tumors occur in the young.

There may be a point of interaction above the pituitary between melatonin and ACTH-corticosteroid secretion. An acute lowering of Cortisol secretion in humans (by metyrapone, for instance) stimulates melatonin secretion. Melatonin also appears to inhibit the release of CRH, thus impinging on the hypothalamic-pituitary-adrenal axis.

When melatonin is low in serum, more CRH is released, culminating in increased Cortisol secretion. Increased Cortisol levels are associated with depression. Interestingly, in bipolar disease it has been reported that serum melatonin would allow for higher levels of Cortisol. In manic states the level of melatonin is high, which should depress release of CRH and generate lower levels of Cortisol. Consequently, melatonin is closely related to the functioning of the hypothalamic-pituitary-adrenal axis and associated psychiatric manifestations (Figure 18-12).

However, there are intermediate situations in which depressed patients also produce normal levels of melatonin, and there are apparently cases of depression, such as the "winter blues" that are more dependent on biorhythm phasing, of which melatonin production can be a marker. Although complex, it is likely that melatonin production will have significance for certain types of depression and for the chronicity of sleep-wake cycles and may play a role in others; melatonin may also be important in this latter type where environmental bright light is a factor. There also seems to be the possibility that, in some cases of depression, high levels of melatonin are produced, but for some reason may not be utilized appropriately (in the hypo-

(dark) or overproduction

Also suppresses GnRH release

Anterior Pituitary

(light) disease state? or hypofunction

(dark) or overproduction

(light) disease state? or hypofunction

Also suppresses GnRH release

Anterior Pituitary

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A Guide to Natural Sleep Remedies. Many of us experience the occasional night of sleeplessness without any consequences. It is when the occasional night here and there becomes a pattern of several nights in arow that you are faced with a sleeping problem. Repeated loss of sleep affects all areas of your life The physical, the mental, and theemotional. Sleep deprivation can affect your overall daily performance and may even havean effecton your personality.

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