Methyldopa Health Dictionary

Prolactin is the pituitary hormone (see PITUITARY GLAND) which initiates lactation. The development of the breasts during pregnancy is ascribed to the action of OESTROGENS; prolactin starts them secreting. If lactation does not occur or fails, it may be started by injection of prolactin.

The secretion of prolactin is normally kept under tonic inhibition by the secretion of DOPAMINE which inhibits prolactin. This is formed in the HYPOTHALAMUS and secreted into the portal capillaries of the pituitary stalk to reach the anterior pituitary cells. Drugs that deplete the brain stores of dopamine or antagonise dopamine at receptor level will cause HYPERPROLACTINAEMIA and hence the secretion of milk from the breast and AMENORRHOEA. METHYLDOPA and RESERPINE deplete brain stores of dopamine and the PHENOTHIAZINES act as dopamine antagonists at receptor level. Other causes of excess secretion of prolactin are pituitary tumours, which may be minute and are then called microadenomas, or may actually enlarge the pituitary fossa and are then called macroadenomas. The most common cause of hyperprolactinaemia is a pituitary tumour. The patient may present with infertility – because patients with hyperprolactinaemia do not ovulate – or with amenorrhea and even GALACTORRHOEA.

BROMOCRIPTINE is a dopamine agonist. Treatment with bromocriptine will therefore control hyperprolactinaemia, restoring normal menstruation and ovulation and suppressing galactorrhoea. If the cause of hyperprolactinaemia is an adenomatous growth in the pituitary gland, surgical treatment should be considered.... prolactin

Inadequate sexual response may be due to a lack of sexual desire (LIBIDO) or to an inadequate performance; or it may be that there is a lack of satisfaction or ORGASM. Lack of sexual desire may be due to any generalised illness or endocrine disorder, or to the taking of drugs that antagonise endocrine function (see ENDOCRINE GLANDS). Disorders of performance in men can occur during arousal, penetration and EJACULATION. In the female, DYSPAREUNIA and VAGINISMUS are the main disorders of performance. DIABETES MELLITUS can cause a neuropathy which results in loss of erection. IMPOTENCE can follow nerve damage from operations on the PROSTATE GLAND and lower bowel, and can be the result of neurological diseases affecting the autonomic system (see NERVOUS SYSTEM). Disorders of satisfaction include, in men, impotence, emission without forceful ejaculation and pleasureless ejaculation. In women such disorders range from the absence of the congestive genital response to absence of orgasm. Erectile dysfunction in men can sometimes be treated with SILDENAFIL CITRATE (Viagra®), a drug that recent research suggests may also be helpful to women with reduced libido and/or inability to achieve orgasm.

Sexual dysfunction may be due to physical or psychiatric disease, or it may be the result of the administration of drugs. The main group of drugs likely to cause sexual problems are the ANTICONVULSANTS, the ANTIHYPERTENSIVE DRUGS, and drugs such as metoclopramide that induce HYPERPROLACTINAEMIA. The benzodiazepine TRANQUILLISERS can reduce libido and cause failure of erection. Tricyclic ANTIDEPRESSANT DRUGS may cause failure of erection and clomipramine may delay or abolish ejaculation by blockade of alpha-adrenergic receptors. The MONOAMINE OXIDASE INHIBITORS (MAOIS) often inhibit ejaculation. The PHENOTHIAZINES reduce sexual desire and arousal and may cause di?culty in maintaining an erection. The antihypertensive drug, methyldopa, causes impotence in over 20 per cent of patients on large doses. The beta-adrenoceptorblockers and the DIURETICS can also cause impotence. The main psychiatric causes of sexual dysfunction include stress, depression and guilt.... sexual dysfunction