Endocrine aspects of male hypogonadism Flashcards
Testosterone
Steroid hormone
Normal young men produce about 7mg each day
In blood is largely bound to plasma protein, with only about 2% present as free hormone
Anatomical units of testes
Seminiferous tubules in which inhibin B and anti-mullerian hormone are synthesised by sertoli cells and sperm are produced
An interstitium containing leydig cells that produce androgens and peritubular myoid cells
Testosterone: 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 involved in spermatogenesis and inhibin B secretion
Testosterone: mechanism of action
Penetrates the target cells whose growth and function it stimulates
Androgen target cells convert testosterone to 5 alpha-dihydrotestosterone before it binds to the androgen receptor
Alternatively, testosterone can be aromatized to oestrogens
Testosterone action
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
Male hypogonadism
Decrease in one or both of the two major functions of the testes: sperm production or testosterone production
Primary hypogonadism
Disease of the testes
Testosterone below normal and the serum LH and/ or FSH are above normal
Secondary hypogonadism
Disease of the hypothalamus or pituitary
Testosterone below normal and the serum LH and/ or FSH are normal or low
Causes of primary hypogonadism
Klinefelter Syndrome
Cryptorchidism
Infection- mump
Radiation
Trauma
Torsion
Idiopathic
Causes of secondary hypogonadism
Congenital GnRH deficiency
Hyperprolactinaemia
GnRH analog
Androgen
Opioids
Illness
Anorexia nervosa
Pituitary disorder
Clinical features of hypogonadism
First trimester- female genitalia to ambiguous genitalia to partial virilisation
Third trimester- micropenis
Prepubertal- failure to undergo or complete puberty
Adults
Symptoms/ signs of hypogonadism
Incomplete sexual development, eunuchoidism
Decreased sexual desire and activity
Decreased spontaneous erections
Breast discomfort, gynaecomastia
Decreased body hair (axillary and pubic)
Very small or shrinking testes
Decreased height, low trauma fracture, low BMD
Decreased muscle bulk and strength
Hot flushes, sweats
Less specific signs/ symptoms
Decreased energy motivation, initiative, aggressiveness, self confidence
Feeling sad or blue, depressed mood, dysthymia
Poor concentration and memory
Sleep disturbance, increased sleepiness
Mild anaemia
Increased body fat, BMI
Diminished physical or work performance
Conditions with a high prevalence of hypogonadism
Sellar mass, radiation to sella, other sella disease
On meds that affect T production or metabolism
HIV associated weight loss
ESRD and maintenance haemodialysis
Moderate to severe COPD
Osteoporosis or low trauma fracture
Type 2 diabetes mellitus
Infertility
Examination
Amount of body hair
Breast exam for enlargement/ tenderness
Size and consistency of testicles
Size of the penis
Signs of severe and prolonged hypogonadism
Arm span
