Prolactin in MRCP

Prolactin in MRCP

I always enjoyed studying endocrinology during my medical school time. One of my old professors said, endocrinology is straight forward and logical. Our body is designed in a way when our hormone level is high, there will be a negative feedback and vice versa. Our bodies try to maintain a normal level of all hormones so that we can function normally.

A trick to remember when you study endocrinology, you must understand normal physiology so that you can understand each hormone clearly and not just memorize them by hard.

OK, today, we will start to learn the first hormone- prolactin. Why prolactin?It is rather interesting that we know prolactin is important for females because it helps in milk production but its function in males remains a mystery!

I think there are a few important facts about prolactin that always asked in your MRCP!

Fact 1:

All hormones in pituitary glands are up regulated by another hormone in hypothalamus ( positive feedback) except prolactin. This means that prolactin production will be inhibited by another hormone prolactin inhibiting hormone ( PIH) from hypothalamus. Remember that PIH is dopamine, therefore your dopamine agonist such as bromocriptine is used to suppress prolactin and thus milk production. ( And also remember that due to its dopaminergic effects, bromocriptine is used in Parkinson’s disease).

Whereas drugs which as anti-dopamin effect such as metoclopramide is used to stimulate prolactin production and it is always used in O+G for post partum mothers if they have problems in milk production.

Fact 2:

You do not believe it, prolactin is a stress hormone. As a medical student, I always do not understand why God created prolactin as stress hormone. Anyway, prolactin level can be measured if you want to differentiate a true seizure from pseudo-seizure because its level is high after an epileptic fit.

Fact 3:

When there is a non-secreting tumour in pituitary causing damage to the stalk, you anticipate secretion of all hormones from pituitary to be reduced ( because positive feedback from hypothalamus) but prolactin level is high because there is no negative feedback from hypothalamus.

Fact 4:

One of the commonest causes of hyperprolactinoma and galactorrhoea is drug-induced and it is due to Phenothiazines!!