Biology of Disease

2 to 5 cm^3 and contains 40 to 500 million sperm. A sperm count of less than

20 million per cm^3 is believed to be subnormal and causes 25% of infertility

cases. In general, the lower the total sperm number the greater the chances of

infertility although men with low counts have been known to father children.

The motility of sperm is also necessary for fertilization to take place and at

least 60% of sperm should have a normal shape and be mobile with beating

flagella.

Investigating infertility involves a clinical and laboratory evaluation of

both partners. Women should be investigated for regular menstruation.

If it is regular, then ovulation is probably occurring. The concentration of

progesterone in plasma is also indicative and should exceed 30 nmol dm–3

on day 21 of the menstrual cycle, values below 10 nmol dm–3 are suggestive

of abnormal ovulation. If ovulation is confirmed then it may be necessary to

examine cervical mucus following intercourse to determine the presence of

motile, normal shaped sperm.

Microscopic examination of samples of ejaculate will indicate whether the

sperm produced are motile and normal in shape or show abnormalities, such

as malformed heads and twin sperm formed by a failure in development.

Sperm counts will show if adequate numbers of sperm are produced. A low

sperm count may be further investigated by measuring the concentrations

of testosterone, FSH and LH in the plasma to compare with their reference

ranges of 9–30 nmol dm–3, 2–10 U dm–3 and 2–10 U dm–3 respectively. In some

cases, a biopsy of the testes may by necessary. Investigation of infertility in

males is outlined in Figure 7.42.

X]VeiZg,/ DISORDERS OF THE ENDOCRINE SYSTEM

&.+ W^dad\nd[Y^hZVhZ

History and examination

Normal sperm count Abnormal sperm count

Measure [testosterone],

[gonadotrophins] and

[prolactin] in serum

Low testosterone

High gonadotrophins

Low testosterone

Low gonadotrophins

Low testosterone

High prolactin

Primary

testicular

failure

Hypogonadotrophic

hypogonadism

Endocrine tests Hyperprolactinemia

not required

Figure 7.42 Overview of the investigation of infertility in males.