Summary. The secretion rates [34 + 6 (SE) ug per day, 9 subjects] and metabolic clearance rates (MCR) [1,288 ± 120 (SE) L of plasma per day, 9 subjects] of aldosterone in elderly subjects are significantly lower than those of young subjects [77 + 7 (SE) Mug per day and 1,631 + 106 (SE) L per day, respectively]. There is a correlation of the MCR and secretion rate values (p = 0.02), but the calculated plasma concentrations (secretion rate/ MCR) are also significantly low in the elderly subjects [2.6 + 0.3 (SE) compared with concentrations in the plasma from young subjects of 4.7 + 0.6 (SE) ug per 100 ml plasma].The urinary excretion of radioactivity from oral and intravenously administered labeled aldosterone as aldosterone in the neutral extract, as aldosterone released by acid hydrolysis, and as tetrahydroaldosterone released by incubation with /-glucuronidase is generally similar for young and elderly subjects except that a larger portion of the oral compared with the intravenous dose is excreted as free aldosterone in the elderly subjects, indicating that the splanchnic extraction is reduced. The calculated splanchnic blood flow (assuming no alteration in extrasplanchnic metabolism) is also slightly lowered.Therefore, as in patients with mild cardiac dysfunction, the lowered MCR of elderly subjects is due to both reduced splanchnic extraction and blood flow. However, unlike the heart failure patients, in the elderly subjects the plasma concentration of aldosterone is also reduced.
: A five‐hour oral glucose tolerance test and simultaneous determinations of serum immunoreactive insulin were performed on 20 male and 20 female elderly nondiabetic subjects whose ages ranged from 68 to 91 years. Results of the glucose tolerance test were abnormal in 29 of the 40 subjects (72.5 per cent) according to accepted standards for young and middle‐aged normal adults. The abnormalities were similar to those found in cases of diabetes mellitus in young adults. The response to glucose stimulation in these elderly subjects was delayed and less efficient than normal. Significant differences were observed with respect to both serum glucose and immunoreactive insulin, the females exhibiting higher levels than the males. Regression analysis showed no immunoreactive insulin in the serum when the glucose level was less than 50 mg per 100 ml.
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