Endocrine

Male hypogonadism

In the male, the testis subserves two principal functions: synthesis of testosterone by the interstitial Leydig cells under the control of luteinising hormone (LH), and spermatogenesis by Sertoli cells under the control of follicle-stimulating hormone (FSH) (but also requiring adequate testosterone)..

Definition

A decrease in either of the two major functions of the testes:
sperm production
testosterone production

CAUSES OF DELAYED PUBERTY AND HYPOGONADISM

Hypogonadotrophic hypogonadism




Hypergonadotrophic hypogonadism




Negative feedback suppression of LH is mediated principally by testosterone, while secretion of another hormone by the testis, inhibin, suppresses FSH

The axis can be assessed easily by a random blood sample for testosterone, LH and FSH. Testosterone is largely bound in plasma to sex hormone-binding globulin,. Testicular function can also be tested by semen analysis.

The clinical features

The clinical features of both hypo- and hypergonadotrophic hypogonadism include loss of libido, lethargy with muscle weakness, and decreased frequency of shaving. Patients may also present with gynaecomastia, infertility, delayed puberty and/or anaemia of chronic disease.

Male hypogonadism is confirmed by demonstrating a low serum testosterone level. The distinction between hypo- and hypergonadotrophic hypogonadism is by measurement of random LH and FSH. Patients with hypogonadotrophic hypogonadism should be investigated as described for pituitary disease on

. Patients with hypergonadotrophic hypogonadism should have the testes examined for cryptorchidism or atrophy and a karyotype performed (to identify Klinefelter's syndrome

Management Testosterone replacement is indicated in hypogonadal men to prevent osteoporosis, and restore muscle power and libido.. First-pass hepatic metabolism of testosterone is highly efficient so bioavailability of ingested preparations is poor. Doses of systemic testosterone can be titrated against symptoms






Testosterone replacement inhibits spermatogenesis. Men with hypogonadotrophic hypogonadism who wish fertility are usually given injections of hCG several times a week (recombinant FSH may also be required in men with hypogonadism of pre-pubertal origin). The duration of gonadotrophin therapy depends on the duration and cause of hypogonadism.

If there is a hypothalamic cause, then pulsatile GnRH therapy is an alternative. Extraction of sperm from the epididymis, in vitro fertilisation and intracytoplasmic sperm injection (ICSI) are being used increasingly to try to achieve fertility in men with primary testicular disease.

GYNAECOMASTIA

Gynaecomastia is the presence of glandular breast tissue in males. Normal breast development in women is oestrogen-dependent, while androgens oppose this effect. Gynaecomastia results from an imbalance between androgen and oestrogen activity, which may reflect androgen deficiency or oestrogen excess

Idiopathic Physiological Drug-induced

Cimetidine Digoxin Anti-androgens, e.g. cyproterone acetate, spironolactone Some exogenous anabolic steroids, e.g. diethylstilbestrol

Investigations If a clinical distinction between gynaecomastia and adipose tissue cannot be made, then ultrasonography or mammography is required. A random blood sample should be taken for testosterone, LH, FSH, oestradiol, prolactin and hCG. Elevated oestrogen concentrations are found in testicular tumor.

Management

An adolescent with gynaecomastia who is progressing normally through puberty may be reassured that the gynaecomastia will usually resolve once development is complete. If puberty does not proceed in a harmonious manner, then there may be an underlying abnormality that requires investigation

Androgen replacement will usually improve gynaecomastia in hypogonadal males and any other identifiable underlying cause should be addressed if possible.