Hypogonadism (male)

Question 1

Definition

Answer 1

A syndrome of decreased testosterone production, sperm production or both

Question 2

Aetiology/Risk factors (primary)

Answer 2

· Primary Hypogonadism

o Gonadal dysgenesis (e.g. Klinefelter’s syndrome, undescended testicles)

o Gonadal damage (e.g. infection, torsion, trauma, autoimmune, iatrogenic)

o Rare causes (e.g. defects in enzymes involved in testosterone synthesis)

Question 3

Aetiology/Risk factors (secondary)

Answer 3

· Secondary Hypogonadism

o Pituitary/Hypothalamic lesions

o GnRH deficiency (Kallmann’s syndrome)

o Hyperprolactinaemia

o Systemic/chronic diseases

o Rare causes: genetic mutations

o Prader-Willi syndrome (short, small hands, almond-shaped eyes, learning difficulty, postnatal hypotonia)

o Laurence-Moon-Biedl syndrome (obesity, polydactyly, retinitis pigmentosa, learning difficulty)

Question 4

Epidemiology

Answer 4

· Primary hypogonadism accounts for 30-40% of male infertility
o Most common cause: Klinefelter’s Syndrome (XXY)

· Secondary hypogonadism accounts for 1-2%

Question 5

Presenting symptoms

Answer 5

· Delayed puberty

· Decreased libido

· Impotence

· Infertility

· Symptoms of underlying cause (e.g. Klinefelters –> intellectual dysfunction, behavioural abnormalities)

Question 6

Signs on physical examination (pre-pubertal)

Answer 6

· Measure testicular volume using Prader’s orchidometer (normal adult volume = 15-25 mL)

· Prepubertal Hypogonadism
o Signs of delayed puberty
· High pitched voice
· Decreased pubic/axillary/facial hair
· Small or undescended testicles
· Small penis
o Gynaecomastia
o Eunuchoid proportions (arm span > height)
o Features of underlying cause (e.g. undescended testicle, anosmia in Kallmann's syndrome)

Question 7

Signs on physical examination (post-pubertal)

Answer 7

· Postpubertal Hypogonadism

o Decreased pubic/axillary/facial hair
o Soft and small eyes
o Gynaecomastia
o Fine perioral wrinkles
o Features of underlying cause (e.g. visual defects if pituitary cause)

Question 8

Investigations (general)

Answer 8

· Serum total testosterone
· Sex hormone binding globulin (SHBG)
· Albumin
· LH and FSH
· Assess bone age (risk of fracture)

Question 9

Investigations (primary)

Answer 9

· Primary Hypogonadism:
o Low testosterone
o High LH and FSH

· Primary - can be investigated using karyotyping (check for Klinefelter’s syndrome)

Question 10

Investigations (secondary)

Answer 10

· Secondary Hypogonadism:
o Low testosterone
o Inappropriately normal/low LH and FSH

· Secondary
o Pituitary function tests
o MRI of the hypothalamic/pituitary area
o Visual field testing
o Smell testing (for anosmia)
o Iron testing (for hereditary haemochromatosis)