Reproductive & Genitourinary System (Phys 2) PDF

Testes Function The male testes has 2 functions: Androgen (testosterone) production Spermatogenesis Hormonal Control of Testicular Function: Hypothalamus: GnRH Anterior pituitary: ○ FSH → Sertoli cells → spermatogenesis (when testosterone present) →...

Testes Function The male testes has 2 functions: Androgen (testosterone) production Spermatogenesis Hormonal Control of Testicular Function: Hypothalamus: GnRH Anterior pituitary: ○ FSH → Sertoli cells → spermatogenesis (when testosterone present) → Inhibin B → neg feedback on FSH ○ LH → Leydig cells → testosterone → neg feedback on LH Testosterone → spermatogenesis and somatic effects TSH, LH, FSH and HCG are structurally similar therefore have similar effects Diseases are characterised by 1˚/2˚ testicular failure 1˚: at testes - Inc FSH/LH, dec testosterone/inhibin 2˚: pituitary or hypothalamus - all hormones dec  Androgen Production Via Leydig Cells in interstitium in response to LH Leads to: ○ Male puberty and virilisation (male characteristics) ○ Spermatogenesis (sertoli cells) Pathway Target Direct pathway Acts directly as Muscle, virilisation testosterone Amplification pathway Converted into DHT via Prostate, skin (androgen receptor) (5-10%) 5-alpha reductase → pubic hair, sebum secretion Diversification pathway Converted into estradiol Brain, bone (estrogen receptor) (0.1%) via aromatase → bone maturation and epiphyseal closure Inactivation pathway Hepatic oxidation/conjugation, renal excretion There is no male menopause - serum testosterone falls 30% between 30-70Y largely due to obesity and chronic disease  Male Puberty Onset: Tanner Staging: 1. Pulsatile GnRH from hypothalamus 2. RIsing LH → leydig cells secrete testosterone → virilisation 3. Testosterone forms metabolites: a. Estradiol - bone b. Dihydrotestosterone - hair and acne Testicular volume: Normal: ○