Prolactin hormone is one of the hormones secreted by the pituitary gland. The most important function of this hormone is to produce milk during lactation. It is also important for normal follicular development and maintenance of corpus luteal secretory activity function. High prolactin levels during lactation inhibit ovulation, the reason for having no periods during lactation. Hence abnormal levels of prolactin causes infertility issues.
Measurement of prolactin hormone
Should be done with 8 to 10 hours of fasting with no breast stimulation. Prolactin should be drawn early in the menstrual cycle – before ovulation. This is because prolactin levels are naturally higher after ovulation. A single elevated reading should be reconfirmed because of the known erratic pattern of secretion. If prolactin levels are borderline high, then three fasting pooled sample is obtained and tested before starting therapy for same. Thyroid function tests should always be performed if prolactin is found to abnormal.
Normal levels of prolactin
- Males: 2 to 18 nanograms per milliliter (ng/mL)
- Nonpregnant females: 2 to 30 ng/mL
- Pregnant females: 10 to 209 ng/mL
Cut off values may vary according to laboratory methods used for detection.
Biological Functions
- To induce and maintain lactation, takes part in reproductive mammary development.
- Responsible for normal follicular development and maintenance of corpus luteal secretory activity function.
- Exerts metabolic effects, and stimulates immune responsiveness.
HYPERPROLACTINEMIA
Hyperprolactinemia is a condition of elevated prolactin levels in blood which could be physiological, pathological, or idiopathic in origin. Similarly elevated prolactin levels could be associated with severe clinical manifestations on one side of the spectrum or be completely asymptomatic on the other side. Its prevalence is 9 to 17% in women with infertility.
Causes of high prolactin levels
- Physiological: Pregnancy, coitus, lactation, REM sleep
- Pituitary adenomas ( tumor of pituitary gland)
- Hypothyroidism
- Polycystic ovarian syndrome
- Stress
- Idiopathic
- Renal / liver failure
- Medications like
- Anti-depressants, Sedatives
- Estrogen
- Oral contraceptives (birth control pills)
- Antihypertensive drugs
- Antacids and antiemetics
Symptoms of hyperprolactinemia
- Nipple discharge
- No periods or irregular periods
- Infertility
- Decreased libido
- Headache, visual symptoms
- Symptoms of hypothyroidism
Hyperprolatinemia may cause infertility in females by several different ways mentioned below.
- High prolactin levels (hyperprolactinemia) : Disrupts normal follicular development, no ovulation, menstrual cycles may cease
- Less severe cases: high prolactin levels may only disrupt ovulation once in a while. This would result in intermittent ovulation or ovulation that takes a long time to occur. Women in this category may experience infrequent or irregular periods
- Mild cases: may ovulate regularly but not produce enough of the hormone progesterone after ovulation. This is known as luteal phase defect. Deficiency in the amount of progesterone produced after ovulation may result in a uterine lining that is less able to have an embryo implant
Prolactin hormone disorders are often missed in male infertility. Hyperprolactinemia causes inhibition in secretion of hormones like FSH, LH, Testosterone which are involved in sperm production, which in turn causes spermatogenic arrest, impaired sperm motility, and altered sperm quality, hence a cause of male infertility.
Treatment of hyperprolactinemia
Prolactin levels can often be corrected by stopping or switching to a different medication if that is the cause. Correction of hypothyroidism is very effective also. Cause of hyperprolactinemia identified should be corrected first.
If prolactin levels are persistently high, they can be effectively treated with a group of medications known as dopamine agonists like bromocriptine and cabergolin.
If prolactin levels are more than 200 ng/dl, MRI Brain has to be done to rule out pituitary adenomas. If diagnosed to have macroadenomas (>10mm size) with symptoms, then surgery or radiotherapy may be essential along with dopamine agonists. Microadenomas of less than 10mm can be managed with dopamine agonists alone.
Any fertility treatment should be initiated after normalizing prolactin levels. If the only cause of infertility is hyperprolactinemia, 60 to 80% pregnancy rates can be achieved with medical therapy alone.
