EFFECTS OF HORMONAL CHANGES
Testosterone
An age-dependent decrease in morning and mean 24-h plasma levels of testosterone occurs; free testosterone levels are less affected. A marked decrease occurs only after the seventh decade. Diet does not seem to influence levels significantly at any age. Smokers have higher testosterone levels than nonsmokers in all age groups, but this difference is not significant in the elderly. In response to stress, serum testosterone levels show greater increases in younger than in older men.
Estrogen
Urinary estrogen increases in elderly men, resulting in an increased estrogen:testosterone ratio. The source of this estrogen appears to be androstenedione, which is metabolized to estrogen by peripheral tissues. Estrogen levels in women decrease after the menopause, the consequences of which are discussed in Ch. 83.
Pituitary and Adrenal Hormones
In general, both pituitary and adrenal function decrease slightly. Decreased pituitary function leads to increased levels of gonadotropins secondary to lower levels of gonadal hormones. Growth hormone levels decrease with aging. Decreased adrenal function may lead to lower circulating levels of Cortisol, although the diurnal pattern is usually preserved.
Serum renin and aldosterone levels fall with age, causing the so-called hyporeninemic hypoaldosteronism state. Together, these changes make hyperkalemia more likely, especially when potassium supplements or potassium-sparing diuretics are administered. Serum vasopressin levels tend to rise with age.
Kndorphin levels increase with age. This may explain the suggestion that elderly persons have a decreased awareness of pain to such events as cardiac ischemia.
Serum concentrations of immunoreactive and bioactive parathyroid hormone increase with age in order to maintain normal serum calcium levels.