19. Endocrine Aspects of Male Hypogonadism Flashcards
(32 cards)
testosterone
steroid hormone secreted in men and women - testes, ovary, adrenals normal men produce ~7mg per day largely protein bound 50% bound to albumin 44% bound to SHBG
testes anatomical units
seminiferous tubules
interstitium
seminiferous tubules
sperm are produced
anti-Müllerian hormone (AMH) and inhibit synthesised by Sertoli cells
interstitium
Leydig cells produce androgens
peritubular myoid cells
androgen synthesis
cholesterol - influenced by LH converted to pregnenolone
converted to progesterone or DHEA
both converted to testosterone
converted either to DHT or estradiol (FSH influence)
hypothalamic-pituitary-testicular axis
pulsatile secretion of GnRH
secretion of LH and FSH
LH involved with testosterone release
FSH involved in spermatogenesis and inhibin B secretion
testosterone mechanism of action
penetrates target cell
converted to 5-alpha dihydrotestosterone (DHT)
DHT can bind to receptor to exert effect - influence gene expression
alternatively, converted to oestrogens
actions of testosterone
regulation of gonadotrophin secretion by hypothalamic pituitary system
initiation and maintenance of spermatogenesis
formation of male phenotype during embryogenesis
promotion of sexual maturation at puberty + maintenance after
increase lean body mass, decrease fat mass
male hypogonadism
decrease in one or both of the 2 major functions of the testes: spermatogenesis and testosterone production
primary causes of male hypogonadism
Klinefelter syndrome cryptorchidism infection-mump radiation trauma torsion idiopathic
secondary causes of male hypogonadism
congenital GnRH deficiency hyperprolactinaemia GnRH analog opioids illness anorexia nervosa pituitary disorder
clinical features in first trimester
female genitalia, ambiguous genitalia, patrol virilisation
clinical features in this trimester
micropenis
clinical features pre-puberty
failure to undergo/complete puberty
clinical features in adulthood
may appear younger than chronological age
decreased libido, depressed mood, small genitalia, decreased muscle mass and hair, infertility
symptoms / signs of male hypogonadism
incomplete sexual development decreased libido breast discomfort, gynaecomastia reduced body hair small/shrinking testes infertility small height decreased muscle bulk and strength
less specific symptoms / signs of male hypogonadism
low energy, motivation, initiative and aggressiveness depressed mood. dysthymia poor concentration and memory sleep disturbance mild anaemia increased body fat
conditions with high prevalence of hypogonadism
sellar mass, radiation to sella and other seller disease
medications affecting T production eg. glucocorticoids, opioids
his-associated weight loss
moderate-severe COPD
osteoporosis
type 2 diabetes
infertility
relevant medical history for male hypogonadism
puberty/sexual development past/present major illness nutrition all drugs relationship/sexual problems major life event s family history recent changes in body testicle problems eating disorders, excessive exercise
examination for male hypogonadism
body hair breast exam for enlargement/tenderness size and consistency of testicles size of penis signs of severe/prolonged hypogonadism (loss of body hair, osteoporosis, reduced muscle strength and bulk) arm span
investigations for male hypogonadism
serum testosterone LH/FSH SHBG LFT semen analysis karyotyping pituitary function MRI DEXA scan
factors lowering SHBG
moderate obesity nephrotic syndrome hypothyroidism drugs e.g. glucocorticoids, progestins, androgens steroids acute illness and malnutrition
factors raising SHBG
ageing hepatic cirrhosis hyperthyroidism anticonvulsants oestrogens HIV infection
testosterone administration
gel
injection
buccal/patch/pellet
