androgen_defic
androgen deficiency
introduction
aetiology:
the male "menopause":
androgens with aging:
iatrogenic androgen deficiency:
other conditions:
Klinefelter's syndrome
myotonic dystrophy:
congenital 5-alpha reductase deficiency:
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):
effects of low androgen levels in the adult male:
osteoporosis
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
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:
investigation:
Rx of male androgen deficiency:
testosterone replacement Rx:
benefits:
improved bone density, muscle strength, improved haemtocrit, reduced adiposity
improved sexual function
improved cognition, decreased depression
risks:
C/I:
options:
parenteral testosterone esters:
cheap, requires injections every 2 weeks, may be painful
rapid peaks & gradual decrease which may effect mood, no circadian variation
trans-scrotal testosterone patch:
requires dry shaving of scrotum; may fall off; worn for 22-24hrs;
expensive, increased scrotal DHT levels, mimics circadian secretion; good clinical response;
trans-dermal testosterone patch:
DHEA replacement Rx:
dehydroepiandrosterone (DHEA) is a weak androgen and is a precursor of both estrogens and androgens
50mg/d may increase bone density, increase muscle strength & decrease adiposity
selective androgen receptor modulators:
references:
androgen_defic.txt · Last modified: 2019/06/17 23:29 (external edit)