Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
The primary physiological function of prolactin is to stimulate breast development in normal women and milk production in nursing mothers. Prolactin values are high at birth and decline rapidly to adult levels by three months. Prolactin concentrations increase markedly during the third trimester of pregnancy and remain elevated after delivery and for as long as nursing continues. Nursing will stimulate the production of prolactin, which in turn will provide for continuous milk and for delay in the resumption of menses.
High levels of prolactin are associated with galactorrhoea and amenorrhoea. Women taking oral contraceptives, or under oestrogen therapy, may have prolactin levels higher than normal. Prolactin is a stress hormone, with elevated levels being seen in such cases as trauma from surgery and even venepuncture. In addition, prolactin levels are also inherently episodic, showing day to day fluctuations as high as 30%. Prolactin levels are subject to sleep related diurnal variations, with levels increasing during sleep and reaching their lowest a few hours after waking. Very high levels of prolactin are seen in some adenomas of the pituitary termed prolactinomas. The concentration of serum prolactin in these cases can help to differentiate between micro and macroprolactinoma.
Specimen container paediatric:
Serum (SST or plain tube)
Specimen container adult:
Serum (SST or plain tube)
Minimum volume paediatric:
0.5 mL blood
Minimum volume adult:
1 mL blood
Sample stability:
Unseparated sample: 2 days
Separated sample: 5 days at 15-25°C, 6 days at 2-8°C, 6 month at -20°C
Interpretation:
Pregnancy, lactation, oral contraceptives and renal failure can increase prolactin. Stress (such as that experienced by some patients during examination/venepuncture) can lead to mild elevations in prolactin. A number of medications (usually those acting as dopamine antagonists) can cause elevations in prolactin. All samples with prolactin concentrations above 700 mU/L will be screened for the presence of macroprolactin. This is immunoglobulin-bound prolactin which, although not biologically active, can be detected by prolactin assays.
Reference ranges:
Female:
>1 year: 102 – 496 mU/L
Male:
>1 year: 86 – 324 mU/L
Factors affecting result:
The presence of macroprolactin can cause misleading increase in prolactin. Macroprolactin screen is performed by the laboratory.
Other info:
Lithium heparin plasma samples also acceptable