Melatonin does not inhibit hypothalamic-pituitary-adrenal activity in waking young men

Multiple signaling pathways convey central and peripheral signals to regulate pituitary function: Lessons from human and non-human primate models

The anterior pituitary gland is a key organ involved in the control of multiple physiological functions including growth, reproduction, metabolism and stress. These functions are controlled by five distinct hormone-producing pituitary cell types that produce growth hormone (somatotropes), prolactin (lactotropes), adrenocorticotropin (corticotropes), thyrotropin (thyrotropes) and follicle stimulating hormone/luteinizing hormone (gonadotropes). Classically, the synthesis and release of pituitary hormones was thought to be primarily regulated by central (neuroendocrine) signals. However, it is now becoming apparent that factors produced by pituitary hormone targets (endocrine and non-endocrine organs) can feedback directly to the pituitary to adjust pituitary hormone synthesis and release. Therefore, pituitary cells serve as sensors to integrate central and peripheral signals in order to fine-tune whole-body homeostasis, although it is clear that pituitary cell regulation is species-, age- and sex-dependent. The purpose of this review is to provide a comprehensive, general overview of our current knowledge of both central and peripheral regulators of pituitary cell function and associated intracellular mechanisms, focusing on human and non-human primates.

Salivary cortisol and melatonin levels in children with frequent episodic tension-type headache do not differ from healthy children

AIM

To investigate the differences in cortisol and melatonin concentrations between children with frequent episodic tension-type headache (FETTH) and healthy children.

METHODS

Forty-four children, 12 boys/32 girls (age: 9 ± 2 years) with FETTH associated to peri-cranial tenderness and 44 age- and sex- matched healthy children participated. Both salivary cortisol and melatonin concentrations were collected from non-stimulated saliva following standardized guidelines. A headache diary for 4 weeks was used for collecting intensity, frequency and duration of headache.

RESULTS

No significant differences for cortisol (t = -0.431; p = 0.668), and melatonin (z = -1.564; p = 0.118) concentrations and salivary flow rate (z = -1.190; p = 0.234) were found between both groups. No significant effect of age or gender was found. In addition, no significant association between cortisol-melatonin concentrations and between cortisol-melatonin concentrations and headache clinical parameters were found.

CONCLUSION

These results suggest that children with FETTH, at first instance, do not present deficits in the secretion of these cortisol and melatonin. Prospective longitudinal studies are needed to further elucidate the direction of current findings, particularly the synchronism of cortisol and melatonin and the course of the headache.

Melatonin improves memory acquisition under stress independent of stress hormone release

RATIONALE

Animal studies suggest that the pineal hormone melatonin influences basal stress hormone levels and dampens hormone reactivity to stress.

OBJECTIVES

We investigated whether melatonin also has a suppressive effect on stress-induced catecholamine and cortisol release in humans. As stress hormones affect memory processing, we further examined a possible accompanying modulation of memory function.

MATERIALS AND METHODS

Fifty healthy young men received a single oral dose of either 3 mg melatonin (n = 27) or placebo medication (n = 23). One hour later, they were exposed to a standardized psychosocial laboratory stressor (Trier Social Stress Test). During stress, subjects encoded objects distributed in the test room, for which memory was assessed a day later ("memory encoding under stress"). Fifteen minutes following stress, memory retrieval for words learnt the day before was tested ("memory retrieval after stress"). Plasma epinephrine and norepinephrine levels, salivary free cortisol levels and psychological responses (attention, wakefulness) were repeatedly measured before and after stress exposure.

RESULTS

Melatonin specifically enhanced recognition memory accuracy of objects encoded under stress (p < 0.001). In contrast, 15 min after stress, when cortisol levels were highest, retrieval of memories acquired the day before was not influenced by melatonin. Moreover, melatonin did not influence stress-induced elevation of catecholamine and cortisol levels which in turn did not correlate with the effects of melatonin on memory.

CONCLUSIONS

The findings point to a primary action of melatonin on central nervous stimulus processing under conditions of stress and possibly on memory consolidation and exclude any substantial suppressive action of the substance on hormonal stress responses.