Male Infertility

Question 1

how is infertility defined?

Answer 1

failure to achieve a clinical pregnancy after 12 months of regular unprotected sex in a couple who have never conceived a child

Question 2

how common is subfertility?

Answer 2

1 in 6 couples

only half of these need assisted conception

Question 3

primary vs secondary infertility?

Answer 3

primary = couple have never conceived 
secondary = have had previous pregnancy (including miscarriage, ectopics and terminations)

Question 4

chances of conception within 1 year in a healthy couple with no known infertility problems?

Answer 4

80%

Question 5

where are sertoli cells found?

Answer 5

cells within the seminiferous tubules in the testes

Question 6

role of sertoli cells?

Answer 6

creates blood-testes barrier (protects spermatozoa from antibodies)
provide nutrients for developing sperm cells
destroy defective sperm cells
remove excess cytoplasm from seminiferous tubules
secrete seminiferous tubule fluid, androgen binding globulin, inhibin and activin

Question 7

what does seminiferous tubule fluid do?

Answer 7

helps carry spermatozoa to epididymis

Question 8

what does androgen binding globulin do?

Answer 8

essential for sperm production (binds to testosterone)

Question 9

what do activin and inhibin do?

Answer 9

regulate FSH secretion and control of spermatogenesis

Question 10

where does spermatogenesis occur?

Answer 10

inside seminiferous tubules

Question 11

describe the path developing sperm take within male genital tract?

Answer 11

spermatogenesis occurs in seminiferous tubules
developing sperm are collected in rete testes and transported to epididymis for storage and maturation
spermatozoa pass from epididymis to urethra via vas deferens

Question 12

what is the vas deferens?

Answer 12

muscular tube continuous with tail of epididymis which travels with the spermatic cord through inguinal canal, passes the bladder and joins the seminal vesicle and forms the ejaculatory duct which joins into the urethra

Question 13

what is the bulbourethral gland (cowpers gland)?

Answer 13

gland which produces and releases fluid which lubricates urethra and neutralises any acidity prior to ejaculation

Question 14

what does seminal vesicle do?

Answer 14

Produces and releases majority of seminal
fluid, containing:
• Fructose (nourishes sperm cells)
• Prostaglandins (Triggers contraction
of vaginal muscles for sperm
motility)
• Fibrinogens (Clot precursors)

Question 15

what does prostate do?

Answer 15

Produces and releases:
• Acid phosphatase
• Citric acid
• Inositol
• Calcium, zinc and magnesium

Question 16

describe hormonal control of spermatogenesis?

Answer 16

GnRH released in pulsatile manner every 2-3 hrs from hypothalamus > GnRH stimulates anterior pituitary to release FSH and LH > LH stimulates testosterone secretion from leydig cells > FHS and testosterone together stimulate spermatogenesis in seminiferous tubules
inhibin released by sertoli cells reduced FSH and testosterone decreases GnRH secretion which decreases LH (Negative feedback) which inhibits spermatogenesis again

Question 17

describe development of sperm (spermatogenesis)?

Answer 17

diploid primordial germ cell > diploid spermatogonia > diploid spermatocytes > meiosis 1 > haploid secondary spermatocytes > meiosis 2 > haploid spermatids > tails and acrosomes are formed > fully formed spermatozoa

Question 18

role of acrosome?

Answer 18

around head of sperm

contains enzymes for penetrating the ovum

Question 19

how are sperm attracted to oocyte?

Answer 19

chemoattraction (Sperm follows conc gradient of chemoattractant secreted by oocyte)

Question 20

what is capacitation?

Answer 20

the series of biochemical and electrical events that take place to allow the
sperm cell to penetrate the cell layer that surrounds the oocyte, by giving the sperm cell the
ability to bind to the zona pellucida via the acrosome reaction

Question 21

describe the changes that occur during capacitation?

Answer 21

sperms tail movement increases in speed and strength

changes in sperm cell membrane to allow acrosomal reaction

Question 22

what happens in acrosomal reaction? (3 steps)

Answer 22

1. specific cell surface glycoproteins (ZP3) of the zona
   pellucida interact with the sperm cell, allowing calcium to enter the spermatozoa, increasing
   the intracellular cAMP.
2. Acrosome then swell and allows enzymes from the acrosome to
   be released.
3. Another glycoprotein in the zona pellucida (ZP2) holds the sperm in place while
   these enzymes are released from the acrosome, allowing the tail to propel the sperm into the oocyte and the enzymes to create the fusion of the sperm to the zona pellucida.

Question 23

3 categories of male factor infertility?

Answer 23

idiopathic (most common)
obstructive
non-obstructive

Question 24

obstructive causes of male infertility?

Answer 24

cystic fibrosis (often have bilateral obstruction or absence of vas deferens)
vasectomy (vas deferens is cut and sealed shut)
both will have normal sperm production etc

Question 25

how are hormones affected in obstructive male infertility?

Answer 25

normal LH, FSH and testosterone

Question 26

non-obstructive causes of male infertility?

Answer 26

cryptorchidism 
chromosomal abnormalities 
infections
endocrine disorders
pathological causes such as testicular tumour
specific sperm abnormalities

Question 27

what is cryptorchidism?

Answer 27

one or both testes being undescended into the dependant part of scrotal sac
(usually descend by 6-9 months)
testes arent ideal environment for sperm production ( too warm)

Question 28

ideal temp for spermatogenesis?

Answer 28

2-4 degrees

Question 29

where may undescended testes be found?

Answer 29

upper scrotum
inguinal canal
intra-abdominal
can have no testes at all (anorchia)

Question 30

who is cryptorchidism more common in?

Answer 30

premature babies
low birth weight
small for gestational age

Question 31

what chromosomal abnormalities can cause non-obstructive male infertility?

Answer 31

klinefelters (47 XXY)
microdeletions of Y chromosome (missing genes on Y chromosome)
robertsonian translocation (extra or missing chromosomes)

Question 32

features of klinefelters?

Answer 32

47 XXY
genetic male
tall
slight developmental delays including motor control, learning and socialising as a child
redued facial hair
poor muscle tone
gynaecomastia in puberty
small penis and testicles

Question 33

how can infection cause non-obstructive infertility?

Answer 33

mumps can cause obstructive or non-obstructive
can have testicular swelling which can block pathways
swelling can also damage seminiferous tubules and affect sperm production (short term, only lasts a few months)
some STIs can cause epididymitis and orchitis which can effect morphology, motility and quantity of sperm produced

Question 34

endocrine causes of non-obstructive infertility?

Answer 34

pituitary tumours and hypothalamus disorders (decreased FSH, LH, testosterone)
thyroid disorders (hyper = decreased sexual function, hypo = increased prolactin production)
diabetes (decreased sexual function and testosterone)
CAH (increased testosterone)

Question 35

how can steroid abuse affect fertility?

Answer 35

can result in decreased FSH, LH and testosterone

Question 36

how can testicular cancer affect fertility?

Answer 36

tumour itself and its treatment
the cancer can change levels of testosterone and cause genetic damage to sperm cells
tumour can also damage tubules or cause obstruction
chemo/radiotherapy can affect spermatogenesis (short term)

Question 37

give an example of a specific sperm abnormality which can cause non-obstructive infertility?

Answer 37

globozoospermia

sperm have rounded heads instead of oval and no acrosome so cant undergo capacitation

Question 38

general hormone changes in non-obstructive infertility?

Answer 38

high FSH and LH
low testosterone
(not always)