Circadian endocrine time structure in humans above 80 years of age

The circadian rhythms in blood hormone concentrations of 17 pituitary, adrenal, pancreatic, testicular, and thyroid hormones were determined in 9 women and 5 men 81 to 91 years of age. Six samples over a 24-hr span were studied for each hormone. Even with the small sample available, 9 of the 17 hormones determined showed a statistically significant circadian rhythm as a group phenomenon (prolactin, estradiol, 17-hydroxyprogesterone, insulin, C-peptide, thyroid stimulating hormone, aldosterone, cortisol, dehydroepiandrosterone sulfate). No rhythm detection by population mean cosinor analysis at the .05 level was obtained in this relatively small group of subjects for adrenocorticotropic hormone, follicle stimulating hormone, growth hormone, luteinizing hormone, triiodothyronine, thyroxine, progesterone (determined in women only) and testosterone (determined in men only).