Endocrine Aspects of Male Hypogonadism Flashcards
Testosterone is a … hormone
steroid
Testosterone is secreted in both men and women, where?
testes, ovaries, adrenals
- Normal young men produce how much testosterone a day?
- how much is derived from adrenal secretions?
- 7mg
- less than 5% is derived from adrenal secretions
- Testosterone in blood is largely bound to … protein, with only about …% present as free hormone
- about … is bound to albumin
- …% is bound to sex hormone-binding globulin
- Testosterone in blood is largely bound to plasma protein, with only about 2% present as free hormone
- about half is bound to albumin
- 44% is bound to sex hormone-binding globulin
The Testes contain two anatomical units:
- … tubules in which inhibin B and anti-Mullerian hormone are synthesized by Sertoli cells and sperm are produced
- An … containing Leydig cells that produce androgens and peritubular myoid cells
- Seminiferous tubules in which inhibin B and anti-Mullerian hormone are synthesized by Sertoli cells and sperm are produced
- An interstitium containing Leydig cells that produce androgens and peritubular myoid cells
Seminiferous tubules - part of testes
- inhibin B and anti-Mullerian hormone are synthesized by … cells and … are produced
inhibin B and anti-Mullerian hormone are synthesized by Sertoli cells and sperm are produced
What is a Sertoli cell?
A Sertoli cell is a “nurse” cell of the testicles that is part of a seminiferous tubule and helps in the process of spermatogenesis, the production of sperm.
What are Leydig cells?
- Leydig cells are interstitial cells located adjacent to the seminiferous tubules in the testes.
- The best-established function of Leydig cells is to produce the androgen, testosterone, under the pulsatile control of pituitary luteinizing hormone (LH)
What are peritubular myoid cells?
A peritubular myoid (PTM) cell is one of the smooth muscle cells which surround the seminiferous tubules in the testis
Androgens are synthesized from … and are produced primarily in the … (testicles and ovaries) and also in the … glands
Androgens are synthesized from cholesterol and are produced primarily in the gonads (testicles and ovaries) and also in the adrenal glands.
Androgens: Synthesis
- … is needed to convert cholesterol to pregnenolone
- pregnenolone is converted either to … or D…
- these converted to testosterone
- once these are in circulation - 5alpha reductase converts testosterone into …
- Or, aromatase converts it into … (… required)
- LH is needed to convert cholesterol to pregnenolone
- pregnenolone is converted either to progesterone or DHEA
- these converted to testosterone
- once these are in circulation - 5alpha reductase converts testosterone into DHT
- Or, aromatase converts it into estradiol (FSH required)
Testosterone: The hypothalamic-pituitary-testicular axis
- In the hypothalamus there is … secretion of … - acts on pituitary leading to …
- Secretion of LH and FSH
- LH and FSH are composed of … glycoprotein chains
- LH is involved in release of …
- FSH is involved in … and Inhibin B …
- In the hypothalamus there is pulsatile secretion of GnRH - acts on pituitary leading to …
- Secretion of LH and FSH
- LH and FSH are composed of two glycoprotein chains
- LH is involved in release of Testosterone
- FSH is involved in spermatogenesis and Inhibin B secretion
Testosterone: Mechanism of Action
- Like other … hormones, testosterone penetrates the target cells whose growth and function it stimulates
- Androgen target cells generally convert testosterone to … before it binds to the androgen receptor
- Alternatively, testosterone can be … to …, which exerts effects that are independent of, opposite to, or synergistic to those of androgen
- Like other steroid hormones, testosterone penetrates the target cells whose growth and function it stimulates
- Androgen target cells generally convert testosterone to 5-alpha dihydrosterone befire it binds to the androgen receptor
- Alternatively, testosterone can be aromatized to estrogens, which exerts effects that are independent of, opposite to, or synergistic to those of androgen
Testosterone action
- regulation of … secretion by the hypothalamic-pituitary system
- initiation and maintenance of …
- formation of the … phenotype during embryogenesis
- promotion of sexual … at puberty and it’s maintenance thereafter
- increase in … body mass and decrease in … mass
- regulation of gonadotropin secretion by the hypothalamic-pituitary system
- initiation and maintenance of spermatogenesis
- formation of the male phenotype during embryogenesis
- promotion of sexual maturation at puberty and it’s maintenance thereafter
- increase in lean body mass and decrease in fat mass
Why is testosterone important?
- sharper …
- increased … mass
- strong …
- pleny of ….
- confidence
- sharper mind
- increased muscle mass
- strong bones
- pleny of energy
- confidence
Male hypogonadism is defined as decrease in one or both of the two major functions of the testes - what are these?
sperm production or testosterone production
Disease of testes is what type of hypogonadism?
primary hypogonadism
Disease of the hypothalamus or pituitary is what type of hypogonadism?
secondary hypogonadism
Primary hypogonadism:
- Testerone levels are below normal and the serum … and/or … are above normal
Secondary hypogonadism:
- Testerone levels are below normal and the serum … and/or … are normal or low
- Testerone levels are below normal and the serum LH and/or FSH are above normal
- Testerone levels are below normal and the serum LH and/or FSH are normal or low
Causes of Primary Hypogonadism:
- … syndrome is most common
- a condition in which one or both of the testes fail to descend from the abdomen into the scrotum - what is this called?
- Idiopathic causes
- Torsion
- Trauma
- Radiation
- Infection - such as …
- Klinefelter syndrome is most common
- Cryptochidism
- Idiopathic
- Torsion
- Trauma
- Radiation
- Infection - mumps