Male Reproductive Physiology Flashcards
Function of testes?
- Sperm production
- Millions of viable sperm produced each day
- Average time from production to ejaculation is 64 days
- Testosterone production
- Maintains male secondary characteristics
- Controls spermatogenesis
What hormone is responsible for male secondary characteristics?
Testosterone
What hormones are involved in the endocrine control of testicular function?
- GnRH
- Gonadotrophin releasing hormone
- Produced from hypothalamus
- Gonadotrophins
- FSH and LH
- Released from anterior pituitary
- Testosterone
- Released from testicles
Where is testosterone produced?
Testicles
Where is gonadorophin releasing hormone produced?
Hypothalamus
Where are the gonadotrophins produced?
Anterior pituitary
What are the gonadotrophin hormones?
FSH and LH
What effects on other hormones does testosterone have?
Inhibits secretion of GnRH by the hypothalamus
Inhibits secretion of FSH and LH by pituitary
What does FSH and LH stimulate?
Spermatogenesis and testosterone secretion by the testis
What is spermatogenesis?
Production of sperm from the primordial germ cells
What is the average cycle of spermatogenesis?
64 days
What are the 2 phases of spermatogenesis?
- Spermatocytogenesis
- Clonal expansion and maturation through mitotic and meiotic process
- Spermiogenesis
- Differentiation into mature sperm cells
What happens during spermatocytogenesis?
Clonal expansion and maturation through mitotic and meiotic processes
What happens during spermiogenesis?
Differentiation into mature sperm cells
When does spermatogenesis start and for how long does it go on?
Starts and puberty and is lifelong
Describe the chromosomal division during spermatogenesis?
- One mitotic division
- Spermatogonium to primary spermatocyte, diploid chromosomes
- First meiotic division
- Primary spermatocyte to secondary spermatocyte, two cells with haploid chromosome number
- Second meiotic division
- Secondary spermatocyte to spermatic, two cells with haploid chromosome number
- Spermiogenesis
- Maturation of spermatids into functional sperm cells (differentiation)
What are some factors affecting spermatogenesis?
- Medical
- Pretesticular – problem with hormonal control
- Functional – excessive weight loss, gain
- Intracranial tumours, cysts, bleeds
- Prolactinoma
- Medications such as opiates, external testosterone
- Genetic – Kallmann’s syndrome
- Testicular – problem at the site of production
- Surgery – orchidectomy, orchidopexy
- STI
- Mumps orchitis
- Testicular trauma or torsion
- Radiotherapy or chemotherapy
- Genetic – Klinefelter’s, Y chromosome microdeletion
- Pretesticular – problem with hormonal control
- Lifestyle
- Smoking
- Obesity
What are some steps to reduce impacts of factors affecting fertility?
- Improve lifestyle
- Normal BMI, stop smoking, alcohol in limits, diet, occupational exposure
- Optimise medical condition
- Stop medications
- Reduce STI risk and treat promptly if diagnosed
- Fertility preservation
- Sperm freezing prior to surgery or cancer treatment
What is the medical term for low sperm count?
Oligospermia
What are clues of oligospermia from examination/investigations?
- Examination
- High BMI
- Small testicles, varicocele, surgical scar
- Hormonal profile
- Low FSH, LH, prolactin, testosterone (hypothalamus or pituitary cause – hypogonadotropic hypogonadism)
- High prolactin – prolactinoma
- High FSH, LH, but low testosterone (testicular cause – hypergonadotropic hypogonadism)
- Genetic tests
- Abnormal karyotype
- CF
- Microdeletion
- USS testis
- Testicular volume
- Hydrocele
- Varicoceoele
- Cancer
What is high FSH and LH but low testosterone called?
What is the cause?
Hypergonadotropic hypogonadism
Testicular cause
What is low FSH and LH and low testosterone called?
What is the cause?
Hypogonadotropic hypogonadism
Hypothalamus or pituitary cause
