MALE REPRODUCTION AND SEX

Gonadotrophin-releasing hormone (GnRH, also called luteinizing hormone-RH) is released episodically from the hypothalamus (during and after puberty) and stimulates LH and FSH secretion from the anterior pituitary gland. LH stimu-lates testosterone production from Leydig cells of the testis. Testosterone circulates bound to sex hormone-binding globulin and acts via nuclear andro-gen receptors to produce male secondary sex characteristics (growth of

pubic, axillary and facial hair, enlargement of the external genitalia, deepen-ing of the voice, muscle growth and frontal balding) and maintenance of libido. FSH stimulates the testes to produce mature sperm and the inhibins A and B; the latter feed back to the pituitary to inhibit FSH.

Male hypogonadism

Hypogonadism in a male results from disease of the testes (primary hypogo-nadism) or disease of the pituitary or hypothalamus (secondary hypogonad-ism). Occasionally there is a defect in the ability to respond to testosterone (Table 14.5). The clinical features are due to subfertility and androgen defi-ciency. The presentation depends on the age of onset of hypogonadism (Table 14.6). In prepubertal onset the patient presents with delayed puberty and eunuchoid body proportions (long legs relative to upper body and long arms relative to overall height) resulting from the continued growth of long bones, which occurs because of delayed fusion of the epiphyses.

Klinefelter’s syndrome is the most common congenital abnormality causing primary hypogonadism, with an incidence of 1 in 1000 live births. It

Table 14.5 Causes of male hypogonadism
Reduced gonadotrophins (hypothalamic-pituitary disease)
Hypopituitarism
Selective gonadotrophic deficiency (Kallman’s syndrome)
Severe systemic illness
Severe underweight
Hyperprolactinaemia
Interferes with pulsatile secretion of LH and FSH
Primary gonadal disease (congenital)
Anorchia/Leydig cell agenesis
Cryptorchidism (testicular maldescent)
Chromosome abnormality (e.g. Klinefelter’s syndrome)
Enzyme defects: 5α-reductase deficiency
Primary gonadal disease (acquired)
Testicular torsion sickle cell disease
Orchidectomy
Chemotherapy/radiation toxicity
Orchitis (e.g. mumps)
Chronic kidney disease
Cirrhosis/alcohol
Sickle cell disease
Androgen-receptor deficiency/abnormality
Table 14.6 Consequences of androgen deficiency in the male
Loss of libido
High-pitched voice (if prepubertal)
No temporal recession of hair
Thinning and loss of facial, axillary, pubic and limb hair
Loss of erections/ejaculations
Small soft testes
Poorly developed penis/scrotum
Subfertility
Increased height and arm span (if prepubertal)
Decreased muscle bulk
Osteoporosis
Gynaecomastia

is the result of the presence of an extra X chromosome (47, XXY). Accelerated atrophy of the testicular germ cells gives rise to sterility and small firm testes. The clinical picture varies: in the most severely affected there is complete failure of sexual maturation, eunuchoid body proportions, gynaecomastia and learning difficulties.

Congenital deticiency of gonadotrophin-releasing hormone (GnRH) may occur in isolation, or be associated anosmia (absent sense of smell), colour blindness, cleft palate and renal abnormalities, in which case it is referred to as Kallmann's syndrome.

Investigations

A low or low-normal serum testosterone confirms the clinical diagnosis of hypogonadism. Supranormal serum concentrations of FSH and LH indicate that the patient has primary hypogonadism (testicular disease), and normal or low levels of FSH/LH indicate disease of the pituitary or hypothalamus (secondary hypogonadism). Further investigations, e.g. serum prolactin, chromosomal analysis (e.g. to exlude Klinefelter's syndrome), pituitary MRI scan and pituitary function tests, will depend on the likely site of the defect.

Management

The cause can rarely be reversed and the mainstay of treatment is androgen replacement as testosterone. Patients with hypothalamic-pituitary disease are given LH and FSH or pulsatile GnRH when fertility is desired.

Loss of libido and erectile dysfunction

Erectile dysfunction is defined as failure to initiate an erection or to maintain an erection until ejaculation. Erection is the result of increased vascularity of the penis controlled via the sacral parasympathetic outflow; it may be impaired by vascular disease, autonomic neuropathy (most commonly from diabetes mellitus) and nerve damage after pelvic surgery. The nervous path-ways for ejaculation are centred on the lumbar sympathetics, and abnormali-ties may occur with autonomic neuropathy and traumatic nerve damage. Psychological factors, endocrine factors (causes of hypogonadism described above), alcohol and drugs, e.g. cannabis, and diuretics may cause abnormali-ties of both parasympathetic and sympathetic nerves. A careful history and examination will identify the cause in many patients. The presence of noc-turnal emissions and morning erections is suggestive of psychogenic erectile dysfunction.

Offending drugs should be stopped. Phosphodiesterase type-5 inhibitors (sildenafil, tadalafil, vardenafil) which increase penile blood flow are usually first choice for therapy. Other methods of treatment include apomorphine, intracavernosal injections of alprostadil, papaverine or phentolamine, vacuum expanders and penile implants.

Many cases are the result of psychological factors, and the patient may respond to psychosexual counselling.

Gynaecomastia

Gynaecomastia is development of breast tissue in the male. It results from an increase in the oestrogen : androgen ratio (Table 14.7) and is most com-monly a result of liver disease or drug side-effects. Gynaecomastia is also seen in early puberty as a result of relative oestrogen excess, and usually resolves spontaneously. Unexplained gynaecomastia may occur, especially in elderly people, and is a diagnosis of exclusion after examination and investigation. The treatment in other cases is either of the underlying cause or by removal of the drug if possible. Occasionally surgery is needed.

Ebook Essentials of Kumar and Clark's Clinical Medicine, 5e

1. Ethics and communication

Ethics and communication

2. Infectious diseases

Infectious diseases

3. Gastroenterology and nutrition

Gastroenterology and nutrition

4. Liver, biliary tract and pancreatic disease

Liver, biliary tract and pancreatic disease
LIVER BIOCHEMISTRY AND LIVER FUNCTION TESTS
SYMPTOMS AND SIGNS OF LIVER DISEASE
JAUNDICE
HEPATITIS
NON - ALCOHOLIC FATTY LIVER DISEASE (NAFLD)
CIRRHOSIS
COMPLICATIONS AND EFFECTS OF CIRRHOSIS
LIVER TRANSPLANTATION
TYPES OF CHRONIC LIVER DISEASE AND CIRRHOSIS
PRIMARY SCLEROSING CHOLANGITIS
BUDD - CHIARI SYNDROME
LIVER ABSCESS
LIVER DISEASE IN PREGNANCY
LIVER TUMOURS
GALLSTONES
THE PANCREAS
CARCINOMA OF THE PANCREAS
NEUROENDOCRINE TUMOURS OF THE PANCREAS

5. Haematological disease

Haematological disease
ANAEMIA
Assessment and treatment of suspected neutropenic sepsis
HAEMOLYTIC ANAEMIA
INHERITED HAEMOLYTIC ANAEMIAS
ACQUIRED HAEMOLYTIC ANAEMIA
MYELOPROLIFERATIVE DISORDERS
THE SPLEEN
BLOOD TRANSFUSION
THE WHITE CELL
HAEMOSTASIS AND THROMBOSIS
THROMBOSIS
THERAPEUTICS

6. Malignant disease

Malignant disease
MYELOABLATIVE THERAPY AND HAEMOPOIETIC STEM CELL TRANSPLANTATION
THE LYMPHOMAS
THE PARAPROTEINAEMIAS
PALLIATIVE MEDICINE AND SYMPTOM CONTROL

7. Rheumatology

Rheumatology
COMMON INVESTIGATIONS IN MUSCULOSKELETAL DISEASE
COMMON REGIONAL MUSCULOSKELETAL PROBLEMS
BACK PAIN
OSTEOARTHRITIS
INFLAMMATORY ARTHRITIS
THE SERONEGATIVE SPONDYLOARTHROPATHIES
Clinical features, Investigations
INFECTION OF JOINTS AND BONES
AUTOIMMUNE RHEUMATIC DISEASES
SYSTEMIC INFLAMMATORY VASCULITIS
DISEASES OF BONE
THERAPEUTICS

8. Water, electrolytes and acid–base balance

WATER AND ELECTROLYTE REQUIREMENTS
BODY FLUID COMPARTMENTS
REGULATION OF BODY FLUID HOMEOSTASIS
PLASMA OSMOLALITY AND DISORDERS OF SODIUM REGULATION
DISORDERS OF POTASSIUM REGULATION
DISORDERS OF MAGNESIUM REGULATION
DISORDERS OF ACID - BASE BALANCE
THERAPEUTICS

9. Renal disease

Renal disease
INVESTIGATION OF RENAL DISEASE
GLOMERULAR DISEASES
NEPHROTIC SYNDROME
URINARY TRACT INFECTION
TUBULOINTERSTITIAL NEPHRITIS
HYPERTENSION AND THE KIDNEY
RENAL CALCULI AND NEPHROCALCINOSIS
URINARY TRACT OBSTRUCTION
ACUTE RENAL FAILURE/ACUTE KIDNEY INJURY
CHRONIC KIDNEY DISEASE
RENAL REPLACEMENT THERAPY
CYSTIC RENAL DISEASE
TUMOURS OF THE KIDNEY AND GENITOURINARY TRACT
DISEASES OF THE PROSTATE GLAND
TESTICULAR TUMOUR
URINARY INCONTINENCE

10. Cardiovascular disease

COMMON PRESENTING SYMPTOMS OF HEART DISEASE
INVESTIGATIONS IN CARDIAC DISEASE
CARDIAC ARRHYTHMIAS
HEART FAILURE
ISCHAEMIC HEART DISEASE
RHEUMATIC FEVER
VALVULAR HEART DISEASE
PULMONARY HEART DISEASE
MYOCARDIAL DISEASE
CARDIOMYOPATHY
PERICARDIAL DISEASE
SYSTEMIC HYPERTENSION
ARTERIAL AND VENOUS DISEASE
ELECTRICAL CARDIOVERSION
DRUGS FOR ARRHYTHMIAS
DRUGS FOR HEART FAILURE
DRUGS AFFECTING THE RENIN - ANGIOTENSIN SYSTEM
NITRATES, CALCIUM - CHANNEL BLOCKERS AND POTASSIUM - CHANNEL ACTIVATORS

11. Respiratory disease


Respiratory disease
TUBERCULOSISnd
DIFFUSE DISEASES OF THE LUNG PARENCHYMA
OCCUPATIONAL LUNG DISEASE
CARCINOMA OF THE LUNG
DISEASES OF THE CHEST WALL AND PLEURA
DISORDERS OF THE DIAPHRAGM

12. Intensive care medicine

Intensive care medicine

13. Drug therapy, poisoning, and alcohol misuse

Drug therapy, poisoning, and alcohol misuse

14. Endocrine disease

Endocrine disease
PITUITARY HYPERSECRETION SYNDROMES
THE THYROID AXIS
MALE REPRODUCTION AND SEX
FEMALE REPRODUCTION AND SEX
THE GLUCOCORTICOID AXIS
THE THIRST AXIS
DISORDERS OF CALCIUM METABOLISM
DISORDERS OF PHOSPHATE CONCENTRATION
ENDOCRINOLOGY OF BLOOD PRESSURE CONTROL
DISORDERS OF TEMPERATURE REGULATION
THERAPEUTICS

15. Diabetes mellitus and other disorders of metabolism

DIABETES MELLITUS
DIABETIC METABOLIC EMERGENCIES
COMPLICATIONS OF DIABETES
SPECIAL SITUATIONS
HYPOGLYCAEMIA IN THE NON - DIABETIC
DISORDERS OF LIPID METABOLISM
THE PORPHYRIAS

16. The special senses

THE EAR
THE NOSE AND NASAL CAVITY
THE THROAT
THE EYE

17. Neurology

COMMON NEUROLOGICAL SYMPTOMS
COORDINATION OF MOVEMENT
THE CRANIAL NERVES
COMMON INVESTIGATIONS IN NEUROLOGICAL DISEASE
UNCONSCIOUSNESS AND COMA
STROKE AND CEREBROVASCULAR DISEASE
EPILEPSY AND LOSS OF CONSCIOUSNESS
NERVOUS SYSTEM INFECTION AND INFLAMMATION
HYDROCEPHALUS
HEADACHE, MIGRAINE AND FACIAL PAIN
SPINAL CORD DISEASE
DEGENERATIVE NEURONAL DISEASES
DISEASES OF THE PERIPHERAL NERVES
MUSCLE DISEASES
MYOTONIAS
DELIRIUM
THERAPEUTICS

18. Dermatology

Dermatology

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