الفهرس 
DefinitionOnly 14 pages are availabe for public view
 |  | from | 169 |  |  |
| | | from | 169 | | |
Abstract
LOH could be defined as a clinical and biochemical syndrome associated with advancing age and characterized by a deficiency in serum androgen levels with or without a decreased sensitivity to androgens. It may result in significant alterations in the quality of life and adversely affect the function of multiple organ systems.
Circulating testosterone concentrations are a function of testosterone production and clearance rates; the age-related decline in serum testosterone concentrations is primarily a consequence of decreased production rates in older men.
The decline in testosterone production in older men is the result of abnormalities at all levels of the hypothalamic-pituitary-testicular axis.
In men, gonadal function declines in a slow progressive way as part of the normal aging process. Waning T levels represent one facet of a larger endocrine decline in many elderly men, with frequent reductions in secretion of thyroid hormone, growth hormone, and/or insulin-like growth factor.
In general ,total testosterone starts to decrease at age 40 years at a rate of approximately 1% (3.2 ng/dl) yearly. Using total testosterone data, it has been estimate that 21% men aged between 60 and 80 increasing to 35% of men over the age of 80 are hypogonadal.