Sex Hormones Flashcards
Sex steroids are derivatives of?
Cholesterol (like all steroids)
What is the rate limiting step in steroid hormone synthesis?
side chain cleavage
What enzyme converts Pregnenolone to Progetsterone?
3B- Hydroxysterone beta dehydrogenase
Androstenedione gives rise to
Testosterone
Testosterone gives rise to
Estradiol
60% of seminal volume comes from where and consists of what?
Bulbourethral glands, seminal vesicles
-contains prostaglandins, fructose, citric acid
Semen =
sperm + secretions mainly from SV(60%) and Prostate (20%)
What pubertal changes are reversible?
spermatogenesis; size, secretion, content( fructose and citrate) of the sex accessory glands.
Non-reversible changes
voice, height, beard growth, libido, muscle mass
Two major functions of testis
gametogenesis and steroid production
sperm produced where?
seminiferous tubules
Testosterone produced where?
Leydig Cells
Spermatogenesis requires what hormones?
FSH, Testosterone (high conc)
Indirectly need:
LH for testosterone and GNRH for the production of FSH and lH
What are Sertoli cells?
The stimulate spermatogenesis and are the site of action of FSH and Testosterone.
- They provide nutrients to developing sperm and provide a blood brain barrier to many chemicals
- secrete inhibin
- phagocytose dead or developing
What is inhibin and where is it produced?
It is a hormone that is needed to decrease FSH
LH secretion occurs in what kind of pattern?
Pulsatile
LH secretion is required for what?
Testosterone production
Some tissues require testosterone to be metabolized to what?
Dihydrotestosterone (must become DHT) in order to reach the nucleus and produce androgenic actions
Examples of tissues that require transformation to DHT?
fetal formation of prostate and external genitalia
- pubertal enlargement of prostate, hair changes, acne
Processes that do not require change?
- pubertal growth of muscle, penis, scrotum
Testosterone is degraded by what organ?
Liver…excreted in the urine
Conversion to estradiol occurs where
adipose tissue, pituitary, hypothalamus
How is testosterone transported in teh blood?
Gonadal steroid binding globulin
- sex hormone binding globulin (70%)
How much T is free at any given time
3%
Actions of testosterone
- fetal differentiation of male sex organs
- induce changes in tissues at puberty
- Maintain size and function of most male ACCESORY organs ( seminal vesicles, prostate, increase fructose content, volume of secretions)
- Stimulate spermatogenesis
- Stimulate protein anabolism and long bone growth
- sex drive
- feedback to inhibit LH
- thick secretions (acne)
- pubic, axillary, facial hair growth
See slide on negative feedback.
ok. Important to note that testosterone feeds back to downregulate secretion of LH and FSH but it takes a ton of testosterone to downreulate FSH to bodybuilders know when they overdose because FSH decreases and size of testes decreases due to decrease in size of semeinferous tubules
Primary sex organs in the female?
Ovaries
Secondary Sex organs
oviducts, uterus, vagina
Glands: mucous and mammary
Estrogen
Stimulates growth and formation of ovaries and follicles
Low estrogen does what to LH and FSH?
inhibitory
Rising estrogen
stimulatory, leads to mid cycle LH burst that causes ovulation
very high E
inhibitory …used to be used as BC
very low E + progesterone
birth control pills
What effect does E hav eon teh muscle and endothelial surfaces of the oviducts, uterus, vagina
Oviduct: growth of muscle and epithelium
- motility
- ciliary beating
Uterus: Myometrium growth, contractility
Cervical mucus
production of thin, watery, clear mucus
Vagina stimulates growth of mammary glands, branching of ducts, fat deposition, nipples and areolae growth and darkening
ok
