Diagnostic Use
Prolactin measurements may be helpful in the investigation of galactorrhoea, amenorrhoea, infertility or hypogonadism. Mildly raised levels (up to 2 to 3 times the upper reference limit) are common and can be due to many causes.
Causes of a raised prolactin:
- Prolactinoma
- Drugs: All classes of psychotropic drugs, including dopamine-antagonists (phenothiazine-type antipsychotics, antihistamines, and antiemetics e.g. metoclopramide), atypical antipsychotics, anti-depressants (tricyclics, SSRIs, MAOIs), cannabinoids, amphetamines, buspirone, alprazolam, domperidone, alpha-methyldopa, reserpine, verapamil, morphine, H2 antagonists, fenfluramine, physostigmine, estrogens (including OC).
- Physical or psychological stress (illness, anaesthesia, surgery).
- Non-functioning pituitary tumours causing pituitary stalk compression.
- Macroprolactin : an elevated prolactin concentration may be due to the presence of macroprolactin, a biologically inactive prolactin-immunoglobulin complex which is cleared slowly from the plasma. The presence of macroprolactin has no clinical consequences, but may lead to unnecessary investigations. At Middlemore Hospital Laboratory, all samples with a raised prolactin concentration are routinely tested for the presence of macroprolactin. The level of monomeric (biologically active) prolactin is reported, as well as the total prolactin (monomeric prolactin + macroprolactin). If the monomeric prolactin is normal, no further investigations for prolactinoma are necessary.
- Post-seizure: Prolactin may be elevated following a convulsion. Blood needs to be taken within 40 min of the event, and should be compared with a baseline sample taken before the event or a sample taken several hours later. However, a normal prolactin level does not discriminate between partial seizures (complex or simple) and non-epileptic events. The prolactin release may be blunted in the case of repetitive seizures.
- Diurnal variation: prolactin levels are highest in early morning
- Pregnancy: can peak up to 10,000 mIU/L in late pregnancy.
- Lactation: peaks at 10 min. after starting breast feeding
- Sexual intercourse
- Hypothyroidism
- PCO syndrome
Reference Intervals
| MALE AND FEMALE |
|
| 0 – 30 days |
600 – 5000 mIU/L |
| 31 – 60 days |
500 – 3200 mIU/L |
| 2 months – < 9 months |
80 – 2000 mIU/L |
| 9 months- <5 years |
50 – 850 mIU/L |
| 5 years – < 17 years |
40 – 600 mIU/L |
| 17 YEARS AND OLDER |
|
| Male |
< 350 mIU/L |
| Female |
< 500 mIU/L |
|
Conversion factors: mIU/L = ng/mL x 21.2 or mIU/L = ug/L x 21.2
Test Method
Principle: Electrochemiluminescence immunoassay - Sandwich
Analyser: Roche Diagnostics Cobas e801
Reagents: Elecsys Prolactin 2
Uncertainty of Measurement
5% Prolactin and 10% Monomeric prolactin