Hormones Male Flashcards
The anterior lobe of the pituitary gland releases —– in response to GnRH
FSH
LH
GnRH
- Is synthesized in the hypothalamus and carried to the anterior lobe by the hypophyseal portal system.
- Is secreted in pulses that occur at 60 to 90 minute intervals
Testosterone circulates in the blood stream while bound to one of two types of transport proteins
- Gonadal steroid binding globulin GBG - carries about two thirds of testosterone
- Albumins
After testosterone diffuses across the plasma membrane of target cells and binds to an intracellular receptor what happens
The hormone receptor complex then binds to the DNA in the nucleus
In many target tissues some of the arriving testosterone is converted to
Dihydrotestosterone DHT
The best known CNS effects occur in the Developing hypothalamus. There, testosterone apparently programs the hypothalamus centers that are involved with
- GnRH production and the regulation of pituitary FSH and LH secretion
- Sexual behaviors
- Sex drive
In adult males, negative feedback controls the level of testosterone production. Above normal testosterone levels inhibit the release of
GnRH by the hypothalamus, causing a reduction in LH secretion and lowering testosterone levels
Dehydroepiandrosterone DHEA
Is the primary androgen secreted by the Zona reticularis of the adrenal cortex
Is promoted as a wonder drug for increasing vitality, strength, and muscle mass.
High levels of DHEA in women have been linked to an increased risk of ovarian cancer as well to masculinization.
Estradiol
- The plasma of adult males contain a small amount of this estrogenic hormone 2ng/dL
- 70% is formed from circulating testosterone.
- Interstitial cells and nurse cells of the testes secrete the rest.
- Aromatase converts testosterone to estradiol
- Estradiol production increases in older men
