Determinants of Plasma Androgen and Estrogen Levels in Men
Year: 2006
Type: dissertation
Abstract: __Abstract__ \n \nThe steroid hormone testosterone is responsible for the development of the primary and \nsecondary male sex characteristics such as male pattern hair growth, deepening of the voice \nand increased lean body mass. Testosterone is produced in the testicular Leydig cells in \nresponse to stimulation by pituitary derived luteinizing hormone (LH). In its turn the pituitary \nLH secretion is regulated by the hypothalamus. Testosterone will feed back onto the pituitary \nand hypothalamus thereby allowing the hypothalamo-pituitary-testicular (HPG) axis to \nmaintain the plasma testosterone concentration within close limits. The serum testosterone \nconcentration is considered normal when within the reference range as supplied by the \nlaboratory. The lower limit of this reference range represents the 2.5 percentile of testosterone \nlevels of a group of apparently healthy men. However, testosterone levels may vary \nconsiderably between individuals. \nOlder men may have signs and symptoms reminiscent oftestosterone deficiency such as lack \nof libido, erectile dysfunction and lower bone and lean body mass. In older men the mean \ntestosterone concentration in blood is lower compared to young men. The question is whether \nthe above-mentioned symptoms truly represent testosterone deficiency. For an adequate \nanswer to this question a better understanding of the determinants ofthe serum testosterone \nlevel in men is necessary in order to better differentiate between normal and abnormal levels \nin a specific individual. \nIn the body testosterone is converted to estradiol. In the past ten years it has become evident \nthat estradiol is responsible for a number of the effects formerly attributed to testosterone. \nEstradiol has an important role in gaining and maintaining bone mass, closing of the \nepiphyses and the feedback on gonadotropin release by the pituitary. Since estradiol may be a \ndeterminant of the circulating testosterone concentrations but may also be involved in the \ndevelopment ofthe clinical syndrome associated with androgen deficiency, evaluation of \nestradiol levels in men seems appropriate. However, the interpretation of estradiol levels in \nmen is probably even more difficult than the interpretation of testosterone concentrations. \nOnly little is known about the determinants of the estradiol serum concentration in men, its \ninteraction with testosterone and the minimal tissue level needed to prevent symptoms of \nestrogen deficiency. \nTherefore, the aim of the present thesis was to gain more insight into the determinants of the \ntestosterone and estradiol concentrations in men. This information may be helpful when \ninterpreting the serum testosterone and estradiol concentrations of men with symptoms \nreminiscent of androgen deficiency.
Author: Willem de Ronde
Language: English
Subfield: Endocrinology, Diabetes and Metabolism
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2142721303