Male Hypogonadism

A clinical syndrome comprising of signs, symptoms and biochemical evidence of testosterone deficiency

Aetiology

Primary hypogonadism

  • Testes primarily affected
    • Decreased testosterone → decreased negative feedback
    • Anterior pituitary secretes higher amounts of LH/FSH → hypergonadotrophic hypogonadism
    • Spermatogenesis is more affected than testosterone production
Congenital causes
  • Klinefelter's syndrome
  • Cryptorchidism
  • Y-chromosome microdeletions
Aquired causes
  • Testicular trauma/torsion
  • Chemotherapy/radiation
  • Varicocele
  • Orchitis (mumps)
  • Infiltrative diseases e.g. haemochromatosis
  • Medications e.g. glucocorticoids, ketoconazole

Secondary hypogonadism

  • Hypothalamus/pituitary affected, testes capable of normal function
    • LH/FSH low (or inappropriately normal) despite low testosterone → hypogonadotrophic hypogonadism
    • Spermatogenesis and testosterone production are equally affected
Congenital causes
  • Kallmann's syndrome
  • Prader-Willi syndrome
Aquired causes
  • Pituitary damage
    • Tumours
    • Infiltrative disease
    • Infection (TB)
    • Apoplexy
    • Head trauma
  • Hyperprolactinaemia
  • Obesity, diabetes
  • Medications (steriod, opiods)
  • Acute systemic illness
  • Eating disorders, excessive exercise

Clinical presentation

Pre-pubertal onset

  • Small male sexual organs e.g. small testes (volume <5 mL), penis and prostate
  • Decreased body hair, high-pitched voice, low libido
  • Gynaecomastia
  • 'Eunuchoidal' habitus (tall, slim, long arms and legs)
  • Decreased bone and muscle mass
  • +/- symptoms due to cause (e.g. asomnia with Kallmann's syndrome)

Post-pubertal onset

  • Normal skeletal proportions, penis/prostate size and voice
  • Decreased libido, decreased sponaneous erectios
  • Decreased pubic/axillary hair, reduced shaving frequency
  • Decreased testicular volume
  • Gynaecomastia
  • Decreased muscle and bone mass
  • Decreased energy and motivation
  • +/- symptoms due to cause (e.g. pituitary lesion causing visual field defect)

Investigations

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Considerations for measuring testosterone

  • When measuring testosterone, free testosterone is used as SHBG concentration can vary greatly which will affect total testosterone
  • Labs will measure total tesosterone and SHGB and use an algorithm to give the 'calculated free testosterone'
  • Testosterone should always be measured 8-11am (peaks in morning)

Management

Aims of treatment

  • Establish/maintain secondary sexual characteristics
  • Maintain sexual function
  • Improve fertility (where possible)
  • Improve body composition

Testosterone replacement therapy

  • Started under the guidance of endocrinology, once stable can be measured in primary care
  • Various routes of administration are avaliable e.g. gel, oral capsules, IM injection