At a glance
Why get tested?
To determine whether or not your prolactin levels are higher (or occasionally lower) than normal
When to get tested?
When you have symptoms of an elevated prolactin, such as (breast milk production, not during pregnancy) and/or visual disturbances and headaches, as part of investigation for female and male infertility, and for investigation of low testosterone in men
A blood sample drawn from a vein in your arm
Test preparation needed?
What is being tested?
Prolactin is a 23kD sized produced by the lactotroph cells of the pituitary gland, a grape-sized organ found at the base of the brain. Normally present in low amounts in men and non-pregnant women, prolactin's main role is to promote lactation (breast milk production).
Prolactin levels increase throughout pregnancy with peak levels being found at delivery and just after childbirth. During pregnancy prolactin, oestrogen and progesterone stimulate breast milk development. Following childbirth, prolactin helps initiate and maintain the breast milk supply. If a woman does not breastfeed, her prolactin soon drops back to low pre-pregnancy levels. If she does breastfeed, suckling by the infant plays an important role in the production of prolactin. When the baby feeds, this has an effect on the amount of prolactin secreted by the pituitary, and this is turn controls the amount of milk produced.
By around six weeks after delivery, prolactin may return to pre-pregnancy levels even in mothers still feeding infants. This mirrors oestradiol production which falls at the same time. Prolactin response to breast feeding decreases over time, when after months of feeding, prolactin elevation is minimally increased above pre-pregnancy levels.
Besides pregnancy, the most common cause of raised prolactin levels are certain prescribed medications and prolactinomas; prolactin-producing tumours of the pituitary gland. Prolactinomas (lactotroph adenomas) are the most common type of pituitary and are usually . They develop more frequently in women but are also found in men.
Elevations of prolactin may be minimal or extreme in prolactinomas, being up to many thousands of times in relation to the reference range. Other causes of prolactin elevation are usually not extreme, such as with stress, breast feeding, pregnancy and certain drug administration. Occasionally, pituitary adenomas are comprised of two types of cells, lactotroph and somatotroph and can produce growth hormone in conjunction with prolactin. Some adenomas can also occur in a MEN Type 1 (Multiple Endocrine Neoplasia) syndrome.
Problems can arise both from the unintended effects of excess prolactin, such as milk production in the non-pregnant woman (and rarely, man) and from the size and location of the tumour. If the pituitary gland and/or the tumour enlarge significantly it can put pressure on the optic nerve, causing headaches and visual disturbances; and it can interfere with the other hormones that the pituitary gland produces.
In women, prolactinomas can cause infertility and irregular periods; in men, these tumours can cause a gradual loss in sexual function and desire. If left untreated, prolactinomas may eventually damage tissues surrounding them.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.