Twenty-four-hour profiles and sleep-related variations of cortisol, thyrotropin and plasma renin activity in healthy African melanoids.
The 24-h hormone profiles have been well documented in caucasians living in a temperate climate, but they have never been examined in melanoid subjects under equatorial conditions, with a 12-h light-dark cycle in a hot climate. To establish normal data for this population, blood samples were taken at 10-min intervals over 24 h in five healthy young melanoids living in Abidjan (Ivory Coast). Cortisol and thyroid stimulating hormone (TSH) concentrations and plasma renin activity (PRA) were determined by radio-immunoassay and sleep was registered using polysomnography. Data were compared with results obtained in Strasbourg (France) from six healthy aged-matched caucasians. The 24-h profile of cortisol concentration was similar in both groups, with a 2-h phase advance in the melanoids. Nocturnal fluctuations of PRA, strongly linked to the rapid eye movement-non rapid eye movement (REM-NREM) sleep cycles, occurred in both groups, with higher levels in the caucasians in the last 2 h of sleep along with greater amounts of NREM sleep. After an evening increase in TSH, the sleep onset-related decrease seen in the caucasians was not observed in the melanoids. In both groups, increasing concentrations of TSH and cortisol occurred with awakening, decreasing concentrations being observed during slow-wave sleep. As in the caucasians studied in the temperate climates, the melanoid subjects living at the equator showed the same temporal organization of hormone rhythms within the 24-h period and the same relationships between the pulses and specific sleep stages.(ABSTRACT TRUNCATED AT 250 WORDS)
Goichot
B
B
Laboratoire de Physiologie et de Psychologie Environnementales, CNRS, Strasbourg, France.
Buguet
A
A
Bogui
P
P
Montmayeur
A
A
Bourdon
L
L
Dumas
M
M
Brandenberger
G
G
D000328:Adult; D044383:Black People; D002940:Circadian Rhythm / Q000502:physiology*; D007560:Cote d'Ivoire; D003431:Cross-Cultural Comparison; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007700:Kinetics; D008297:Male; D012083:Renin / Q000097:blood*; D012890:Sleep / Q000502:physiology; D013972:Thyrotropin / Q000097:blood*; D013997:Time Factors
D013972:Thyrotropin; D012083:Renin; D006854:Hydrocortisone