T1 L19 : ): Endocrine aspects of male hypogonadism Flashcards
describe testosterone
- type of hormone
- sexes
- how much is normal production in young men
- the percentage distribution that its bound to
Steroid hormones
Secreted both in men and women – Testes, Ovary and Adrenal
Normal young men produce about 7 mg each day, of which less than 5% is derived from adrenal secretions
Testosterone in blood is largely bound to plasma protein, with only about 2 % present as free hormone
- About half (>50%) is bound to albumin,
- 44% is bound to sex hormone-binding globulin (SHBG)
what are the 2 anatomical units of the testes
Seminiferous tubules in which inhibin B and anti-Müllerian hormone are synthesized by Sertoli cells and sperm are produced.
An interstitium containing Leydig cells that produce androgens and peritubular myoid cells.
what is the relationship between the hypothalamic-pituitary testicular axis
- Pulsatile secretion of GnRH
- 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
what is the mechanism of action for testosterone
- Like other steroid hormones, testosterone penetrates the target cells whose growth and function it stimulates
- Androgen target cells generally convert testosterone to 5 α-dihydrotestosterone before it binds to the androgen receptor
- Alternatively, testosterone can be aromatized to estrogens, which exert effects that are independent of, opposite to, or synergistic to those of androgen
what is the mechanism of action for testosterone
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 its maintenance thereafter
Increase in lean body mass and decrease in fat mass
describe male hypogonadism
Decrease in one or both of the two major functions of the testes: sperm production or testosterone production.
Disease of the testes (primary hypogonadism) or disease of the hypothalamus or pituitary (secondary hypogonadism)
Primary hypogonadism: Testosterone below normal and the serum LHand/orFSH are above normal.
Secondary hypogonadism: Testosterone below normal and the serum LHand/orFSH are normal or low.
what are the primary causes of hypogonadism
Klinefelter syndrome Cryptorchidism Infection-mump Radiation Trauma
what are the secondary causes of hypogonadism
Congenital GnRH deficiency Hyperprolactinemia GnRH analog Androgen Opioids Illness
what is a clinical feature of hypogonadism
First trimester – female genitalia to ambiguous genitalia to partial virilization
Third trimester – micropenis
Prepubertal – failure to undergo or complete puberty
Adults
what are the symptoms and signs of hypogonadism
Incomplete sexual development, eunuchoidism
> Sexual desire & activity
> Spontaneous erections
Breast discomfort, gynecomastia
> Body hair (axillary & pubic), shaving
Very small or shrinking testes (esp < 5 ml)
what are the conditions with a high perveance of hypogonadism
Sellar mass, radiation to sella, other sellar disease
On meds that affect T production or metabolism
Glucocorticoids, ketoconazole, opioids
HIV-associated weight loss
ESRD and maintenance hemodialysis
Moderate to severe COPD
what is the relevant medical history of male hypogonadism
-Puberty and sexual development
Past/present major illnesses
Past/present nutritional deficiency
All prescription & nonprescription
drugs
Relationship problems
how do you examine for male hypogonadism
Amount of body hair
Breast exam for enlargement/tenderness
Size and consistency of testicles
Size of the penis
Signs of severe & prolonged hypogonadism
what investigations can we do for male hypogonadism
Serum testosterone
LH/FSH
SHBG
LFT
Semen analysis
what are the guidelines for screening male hypogonad
Initial screen = morning total testosterone
- Levels are highest in the morning
- Normal testosterone is generally age dependent
Confirmation = repeat morning total testosteron
Free or bioavailable
Do not screen during acute or subacute illness
Illness, malnutrition, and certain medications may temporarily lower testosterone
