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Aarre Kivelä


Serum melatonin concentrations from 55 pregnant healthy women (13 during the first, 18 during the second and 24 during the third trimester) and 11 non-pregnant control women were measured radioimmunologically at 11.00 h (Study A). In addition, serum melatonin concentrations from 12 women in early and 11 women in late pregnancy were measured every four hours throughout the day (Study B). Serum melatonin levels during the third trimester of pregnancy (76.5±38.3 pmol/l were significantly (p<0.01) higher than those during the first (29.7±9.9 pmol/l and the second trimester (39.1 ± 11.2 pmol/l and those of non-pregnant control women (41.7± 15.5 pmol/l and there was a positive correlation between the week of gestation and serum melatonin at 11.00 h (Study A). A clear diurnal rhythm in serum melatonin concentrations was found both in early and in late pregnancy (Study B). The amplitude and duration of the nocturnal rise of melatonin were higher during late pregnancy, but there was no clear phase shift. Increased serum concentration of melatonin in late pregnancy may be due to increased synthesis and secretion or retarded metabolism of melatonin during late pregnancy.

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Olli Vakkuri, Aarre Kivelä, Juhani Leppäluoto, Maija Valtonen, and Antti Kauppila

Vakkuri O, Kivelä A, Leppäluoto J, Valtonen M, Kauppila A. Decrease in melatonin precedes folliclestimulating hormone increase during perimenopause. Eur J Endocrinol 1996;135:188–92. ISSN 0804–4643

Melatonin, the hormone of the pineal gland, which in animal studies has been found to inhibit aging processes, is secreted in smaller amounts towards senescence. Menopause, an aging process in women, is known to be associated with typical changes in gonadotropin and sex steroid secretion. Our main objective was to study the possible role of melatonin in the hormonal regulation of menopause. This study focused on detailed changes in melatonin and follicle-stimulating hormone (FSH) secretion cross-sectionally in pre- to postmenopausal females. Special attention was paid to females aged around 50 years, which is the mean menopausal age. Seventy-seven healthy female volunteers aged 30–75 years were the subjects of this study. Melatonin was measured radioimmunologically from nocturnal urine collected between 20.00 and 08.00 h, and FSH and melatonin from blood samples taken at 09.00 h. Nocturnal urinary excretion of melatonin was found to decline significantly from premenopause to postmenopause. The youngest premenopausal women (age group 30–39 years) excreted the highest amounts of melatonin (21.1 ± 2.2 pmol/h, mean±sem, N = 17). In the age group 40–44 years the excretion declined by 41% (p < 0.05). The second significant decline (35%, p < 0.05) took place between the age groups 50–54 years and 55–59 years. A declining trend as a function of age was also seen in morning serum melatonin. Serum FSH rose sharply to high levels before the age of 50 (p < 0.01) and remained at a high level thereafter. Urinary melatonin correlated negatively with serum FSH (r = −0.32. p < 0.05). In conclusion, the inverse changes in melatonin and FSH secretion during the perimenopausal years, with the sharpest decline in nocturnal excretion of melatonin far before menopause, suggest that melatonin may be permissively linked to the initiation of menopause.

O Vakkuri. Department of Physiology. University of Oulu, Kajaanintie 52 A, 90220 Oulu, Finland