? due to increased oestradiol production from increased adiposity
although andropausal men remain fertile, there is a decrease in spermatogenesis and sperm motility with age due to:
a decrease in the number and function of Sertoli cells with ageing, resulting in an increase in follicle-stimulating-hormone levels and a decrease in inhibin levels
female external genitalia & thus raised as girls, but when they reach puberty, circulating testosterone increases & they develop male body, male libido, clitorimegaly (“penis-at-12” syndrome) to the point that some can have intercourse with women. They thus tend to change gender identities & become boys although they tend to have little facial hair or baldness
lack prostate development in fetal and adult life
congenital adrenal hyperplasia:
cholesterol desmolase deficiency results in compromised conversion of cholesterol to pregnenolone, resulting in low cortisone and sex hormone levels, causing diffuse adrenal insufficiency and feminisation with resultant high ACTH levels causing adrenal hyperplasia. Most die soon after birth.
17-alpha hydroxylase deficiency (rare):
no sex hormones produced ⇒ female external genitalia regardless of sex
effects of low androgen levels in the adult male:
osteoporosis
? role of leptins acting on hypothalamus to inhibit bone mineralisation centrally as well as promoting fertility
does obesity help prevent osteoporosis by causing leptin resistance?
sexual dysfunction:
testosterone is necessary for libido, erectile function, and normal ejaculation
oestrogens may have a role in determining sexual function in men (oestrogen is mainly from metabolism of testosterone)
bio-available testosterone levels correlate strongly with nocturnal penile tumescence, especially in men 55 to 64 years of age
in hypogonadal men, testosterone Rx increases penile rigidity and in the number of erectile events per hour.
? association with prostate cancer
loss of anabolic actions:
decrease in muscle strength and mass:
men lose muscle strength with aging
from the fourth decade onward, there is a decrease of 8% to 10% in peak torque per decade
muscle protein synthesis decreases by 55%, and there is a decrease in myosin heavy chain fibers with an increase in the deposition of connective tissue and fat in muscle. The decrease in muscle parallels the decrease in testosterone concentration
men with primary hypogonadism have been shown to develop weakness of limb-girdle muscles
in young hypogonadal men, replacement doses of testosterone increase muscle mass and strength
increase in body fat
abdominal obesity in men is often associated with low serum testosterone concentrations, testosterone administration decreases abdominal fat and increases lean body mass
loss of vascular tone?
high levels of plasminogen activator inhibitor-1, thus inhibiting the fibrinolytic process
decrease in hemoglobin and hematocrit values:
depression & cognitive dysfunction:
bio-available testosterone levels are inversely associated with depression, higher levels of testosterone are also associated with better mental control and long-term verbal memory
in hypogonadal men, testosterone replacement improves mood and sense of well-being, reduces anxiety, and improves concentrating ability
testosterone replacement enhances spatial cognition in elderly men
testosterone reduces neuronal secretion of beta-amyloid peptide, the major protein in plaques of patients with Alzheimer's disease
auto-immune disease
clinical assessment of suspected androgen deficiency:
as many of the features in the elderly are non-specific (eg. fatigue, weakness, depression), history & examination should look for evidence of androgen deficiency and its possible causes:
history:
frequency of shaving, loss of body hair, libido and sexual performance
history of osteoporosis, fractures, and mood changes
headaches, visual complaints, head trauma, testicular trauma or infection, and medications
examination:
inspection of body hair, breast size, visual fields, and genitals
investigation:
early morning serum total testosterone level:
if it is less than 300 ng/dL, the patient should be considered hypogonadal & thus need to exclude treatable causes:
serum prolactin:
elevated prolactin level may indicate the presence of a pituitary tumor
thyroid-stimulating hormone:
if hypothyroid, start Rx with thyroxine as per usual
gonadotropin levels:
low gonadotropin levels indicate central hypogonadism