lec 9 endocrine

Lec:9 Dr.Mohammed Alhamdany
Hyperprolactinaemia/galactorrhoea
Hyperprolactinaemia is a common abnormality which usually presents with hypogonadism and/or galactorrhoea (lactation in the absence of breastfeeding).
The causes of hyperprolactinaemia include:
1- Physiological:
a- Stress. b- Pregnancy. c- Lactation.
2- Drug-induced
A- (Dopamine antagonists)
a- Antipsychotics (phenothiazines).
b- Antidepressants.
c- Antiemetics (e.g. metoclopramide, domperidone).
B- Dopamine-depleting drugs (Methyldopa).
C- Oestrogens ( Oral contraceptive pill ).
3- Pathological: including
1- Disconnection hyperprolactinaemia.
2- Prolactinoma (usually microadenoma).
3- Primary hypothyroidism.
4- Polycystic ovarian syndrome.
5- Macroprolactinaemia( see below).
6- Renal failure.
Macroprolactinaemia
Prolactin usually circulates as a free (monomeric) hormone in plasma, but in some individuals prolactin becomes bound to an IgG antibody. This complex is known as macroprolactin and such patients have macroprolactinaemia. Since macroprolactin cannot cross blood-vessel walls to reach prolactin receptors in target tissues, it is of no pathological significance. Some commercial prolactin assays do not distinguish prolactin from macroprolactin and so macroprolactinaemia is a cause of spurious hyperprolactinaemia. Identification of macroprolactin requires gel filtration chromatography or polyethylene glycol precipitation techniques.
Clinical assessment ((for hyperprolactinaemia)
In women, in addition to galactorrhoea, hypogonadism associated with hyperprolactinaemia causes secondary amenorrhoea and anovulation with infertility, In men there is decreased libido, reduced shaving frequency and lethargy.
Investigation:
Pregnancy should first be excluded before further investigations are performed in women of child-bearing potential. The upper limit of normal for many assays of serum prolactin is approximately 500 mU/L (14 ng/mL). In non-pregnant and non-lactating patients, monomeric prolactin concentrations of 500–1000 mU/L are likely to be induced by stress or drugs, and a repeat measurement is indicated. Levels between 1000 and 5000 mU/L are likely to be due to either drugs, or a microprolactinoma or ‘disconnection’ hyperprolactinaemia.
Levels above 5000 mU/L are highly suggestive of a macroprolactinoma.
Patients with prolactin excess should have tests of gonadal function, and T4 and TSH should be measured to exclude primary hypothyroidism causing TRH-induced prolactin excess. MRI or CT scan of the hypothalamus and pituitary should done for any patient with persistent hyperprolactinaemia. Patients with a macroadenoma also need tests for hypopituitarism.

Prolactinoma
Most prolactinomas in pre-menopausal women are microadenomas because the symptoms of prolactin excess usually result in early presentation.
In prolactinomas there is a relationship between prolactin concentration and tumour size: the higher the level, the bigger the tumour.