When do you check macroprolactin in the evaluation of hyperprolactinemia?  

I always check it for prolactin levels that are abnormal, but below 100 ng/mL. Macroprolactinemia is rather common in mild/moderate hyperprolactinemia, but it is very rare as sole cause of hyperprolactinemia when level is higher than 100 ng/mL. Importantly, even real hyperprolactinemia may appear mo...

Macroprolactin is usually biologically inactive so if a patient has high prolactin without any symptoms, I would check macroprolactin.