SEASONAL-CHANGES IN THE LEVELS OF ANTIDIURETIC-HORMONE AND MELATONIN IN THE ELDERLY

Antidiuretic hormone (ADH) and melatonin in plasma were measured every 4 hr during a 24-hr period in 69 elderly volunteers (42 males and 27 females) aged 75.6 +/- 8.8 years (+/- SD) and 73.5 +/- 9.5 years, respectively. The population was divided into three groups, which were examined February 27-28, April 25-26, and November 14-15. For the males, the mean ADH level during 24 hr was fewest in April and highest in November with a level five times higher than in April. The ADH lever in February was about three times higher that in April. Females did not show any seasonal variation in the ADH system. The melatonin levels were lowest in November, higher in February, and even higher in April in both male and female volunteers. The ADH increased with age in males (R(2) = 0.13; P < 0.05) but not in females (R(2) = 0.07; NS). The melatonin concentration decreased with age for the whole group, aged 60-98 years.