Using gas chromatography-negative ionization mass spectrometry, plasma melatonin levels in pinealectomized and sham-operated rats were assessed. The pinealectomized rats consistently demonstrated an absence of plasma melatonin while the intact animals showed detectable amounts. This suggests that although melatonin may be formed in tissues other than a pineal gland, the contribution to plasma is of pineal origin. Thus, plasma melatonin levels can be used as a marker of circadian melatonin secretion by the pineal gland and of its beta-adrenergic regulation.

In 25 normally non-pregnant women, 543 normally pregnant women and 75 pregnant women with diabetes mellitus or gestational diabetes mellitus, the relationship between the serum concentration of 1,5-anhydro-D-glucitol (1-deoxy-glucose) and carbohydrate metabolism was studied. The concentration of 1,5-anhydro-D-glucitol was estimated by means of gas-liquid chromatography. In normally non-pregnant women the concentration was found to be 18.6 +/- 5.2 mg/l (mean +/- SD). During the normal pregnancy, from 9 weeks of gestation, a steadily decreasing concentration was observed as the pregnancy progressed and the lowest value (10.2 +/- 4.6 mg/l) was found in the third trimester. After 5 days of puerperium the concentrations were found to be 10.8 +/- 3.7 mg/l. On the 30th day postpartum, the level was within the range for non-pregnant subjects. The values in pregnant women with diabetes mellitus and gestational diabetes mellitus were mostly below 10 mg/l throughout the entire pregnant period. The 1,5-anhydro-D-glucitol concentration was not affected by meals or oral glucose loading. A concentration below 10 mg/l was found in 36% of the normally pregnant women, where oral glucose tolerance tests and measurement of glycohemoglobin were shown to be within the normal range. The present study suggests that a change of 1,5-anhydro-D-glucitol level during pregnancy may reflect a mild alteration of carbohydrate metabolism that goes undetected by all the other diabetic indicators.

Daily urinary excretion of conjugated 6-hydroxymelatonin, the major metabolite of the pineal hormone melatonin, has been determined in 54 boys and 47 girls (aged 3-16 yr) and 20 normal adults to determine whether a change in melatonin production is seen during the maturation of reproductive function in humans. There was no correlation between daily excretion rates and age in children, and the excretion rates were similar to those in adults. In addition, children of all ages had normal circadian patterns of 6-hydroxymelatonin excretion from the earliest age tested. A significant increase in 6-hydroxymelatonin excretion was observed at the time of the onset of breast development (Tanner stage II) in girls. No similar difference was seen during puberty in males. The significance of this difference in Tanner II girls is not known.

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