Prolactin: Function and Hyperprolactinemia
Reference Levels of Prolactin
- Normal value: 2–25 ng/ml
- Between 25–200 ng/ml there is a diagnostic uncertainty about the cause of hyperprolactinemia. Prolactin levels > 200 ng/ml speak in favor of a prolactinoma.
Effects of Prolactin
Chemistry of Prolactin
Prolactin is a polypeptide of 199 amino acids, which is released from the anterior lobe of the pituitary gland.
Physiological Trigger for Prolactin Release
- Sucking (by the baby) on the nipple
- Most probably, there is a prolactin releasing hormone (PRH), yet to be identified.
- TRH, oxytocin, angiotensin II, serotonin, endorphin and adrenaline are promoting prolactin release.
Inhibitors of Prolactin Release
- Dopamine, also called prolactin-inhibiting hormone (PIH)
- GHRH, endothelin-1, increased plasma osmolarity (prevention of dehydration of the breastfeeding mother)
Physiological Effects of Prolactin
- Stimulation of the mammary glands to produce milk (pregnancy and lactation)
Inhibition of ovulation (during lactation)
- Induction of the parental care behavior
- Promotion of sexual gratification and sexual refractory period
- Inhibition of GnRH secretion
Differential Diagnosis of Hyperprolactinemia
- Prolactinoma (usually prolactin levels > 200 ng/ml)
- Lack of prolactin inhibitory factor (PIF) = dopamine: Damage to the hypothalamus or pituitary tumors
- Drugs: metoclopramide, estrogen-containing drugs, antidepressants, antipsychotics
- Functional hyperprolactinemia: usually only moderately elevated prolactin levels are caused by stress, pregnancy and lactation, severe renal insufficiency or primary hypothyroidism.
Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
You did not find what you are looking for?
Search this site with Google: