male hypogonadism Flashcards
(23 cards)
What produces testosterone?
Leydig cells
What converts testosterone to its active form?
5 alpha reductase
Explain the HPG axis
- hypothalamus releases GnRH
- This causes the anterior pituitary to synthesise and release LH and FSH
- LH acts on the leydig cells to produce testosterone
- FSH acts on the Sertoli cells to stimulate spermatogenesis
- Testosterone and oestrogen (testosterone converted to oestrogen) decreases release of GnRH and LH and FSH by negative feedback mechanism
What are the biological effects of testosterone?
Growth: •Sex organs •Skeletal muscles •Epiphyseal plates •Larynx growth •Secondary characteristics
Other:
•Erythropoiesis and Hb maintenance
•Behaviour
What are the effects of testosterone in adult men?
•Muscle mass and strength •Mood •Bone mass •Libido •Body shape •Fertility: - libido - erectile function - spermatogenesis
What cells does spermatogenesis involve?
Spermatocytes, leydig and Sertoli cells
What is the role of leydig cells?
Secretes testosterone to promote sperm development
What is the role of Sertoli cells?
- Blood testis barrier
- Remove damaged spermatocytes
- Secrete androgen binding protein to ensure increased testosterone in the testes
What are the clinical features of hypogonadism in children/young adults?
- Slow growth in teens
- No pubertal growth spurt
- Lack of secondary sexual development (small testes/phallus)
What are the clinical features of hypogonadism in adults?
- Low mood
- Poor libido
- Erectile dysfunction
- Hot flashes/sweats
- poor muscle bulk/power
- poor energy
- Sparce body/facial hair
- Gynaecomastia
- Gynoid weight gain
- Short phallus/reduced testicualr volumes
- Low trauma fractures
Explain clinical assessment of hypogonadism
- Symptoms, growth
- Past medical history- any trauma or head injury
- family history, do they have any children?
- Medications/drugs, over the counter or prescribed
- Social history
- any sign of chronic illness
- Height and weight
- secondary sexual characteristics
- Testicular size
Explain the testing for suspected hypogonadism
•Testosterone:
- early morning fasting venous blood sample
- normal: free testosterone>200 or total>10
- SHBG (if low can impact)
- repeat to confirm
•LH and FSH
- determines if pituitary or testicular cause
•Other considerations:
- if concerned about fertility then semen analysis
- ferritin/ACE
- pituitary screen/ MRI of pituitary
- testicular: ultrasound, karyotype
- DEXA
Blood test results in secondary hypogonadism
- Hypogonadotrphic hypogonadism
- LH and FSH normal or low
- Low testosterone
Blood tests in primary hypogonadism
- Hypergonadotrophic hypogonadism
- LH and FSH high
- Low testosterone
What are the causes of hypogonadotrophic hypogonadism?
•Pituitary disease - tumour, pituitary surgery, radiotherapy •Head injury •isolated LH/FSH deficiency - kallmanns •Functional hypothalamic hypogonadism - exercise - weight changes - physical/psychological stress - systemic illness
What is Kallmann’s syndrome?
- Isolated gonadotrophin deficiency
- Failure of cell migration of GnRH cells to the hypothalamus
- Associated with aplasia or hypoplasia of the olfactory bulbs - anosmia or hyposmia
- Associated with deafness, renal agenesis, cleft lip/palate
Explain the diagnosis of Kallmann’s syndrome
- Anosmia in 75%
- Low testosterone, LH/FSH
- Normal rest of pituitary function
- Normal pituitary MRI but absent olfactory bulb
What are the genetics of Kallmann’s?
- Most commonly an isolated gene mutation
- X linked - absence of KAL 1
- Autosomal dominant KAL2
- Autosomal recessive KAL3
What are the primary gonadal diseases?
- Chromosome defects e.g. Kleinfelter’s
- Seminiferous tubule or adult leydig cell failure e.g. following trauma, chemo-therapy or part of multi system disorder
- Cryptorchidism
What is Klinefelter’s?
- Most common cause of male hypogonadism
- Karyotype: 47XXY or 47XXY mosaicism
- Clincially manifests at puberty
- Elevated LH/FSH but seminiferous tubules regress and leydig cells do not function normally, low testosterone
What is the presentation of Klinefelter’s?
Clinical variation in phenotype •Delayed puberty •Reduced testicular volumes •Reduced secondary male characteristics •Persistent gynaecomastia •Azospermia •Behavioural issues/learning difficulties
What is the management of Kleinfelters?
•Androgen replacement - IM testosterone or topical •Psychological support •Fertility counselling - hCG, recombinant FSH and LH, GnRH pumps
What are the side effects of testosterone?
- Mood issues (aggression/behaviour change)
- Libido issues
- Increased haematocrit/polycythaemia
- Possible development of lower urinary tract symptoms
- Acne
- Gynaecomastia due to increased oestrogen
