Prolactin and infertility | Interpretation of prolactin levels

What is Prolactin?

Prolactin is a hormone that is secreted by your pituitary gland, a pea-sized gland found below the brain. Prolactin is found in both men and women and is released at various times throughout the day and night. As the name suggests, the role of prolactin is to stimulate milk production in pregnant women. It also enlarges a woman's mammary glands in order to allow her to prepare for breastfeeding.

Prolactin and Infertility

Prolactin doesn't just cause your body to increase milk production - it also affects your ovulation and menstrual cycles. (This is why women who are breastfeeding rarely get pregnant). Prolactin inhibits two hormones necessary for ovulation: follicle-stimulating hormone (FSH) and gonadotropin-releasing hormone (GnRH). When you have high levels of prolactin in your blood (a condition called hyperprolactinemia), you will not ovulate and this will result in infertility. This anovulation can also cause you to have irregular cycles.

Normal levels.

The normal values for prolactin are:

  • Males: 2 - 18 ng/mL
  • Nonpregnant females: 2 - 29 ng/mL
  • Pregnant women: 10 - 209 ng/mL

Prolactin levels are measured using different units in different laboratories, and this can cause considerable confusion. Traditionally, prolactin levels were measured in ng/ml, and normal prolactin levels in women are less than 29 ng/ml.

The new units are pmol/l and to convey you need to multiply by 44. This means the normal level is less than
700 pmol/l or mIU/L

A low level is of no clinical importance.

High prolactin levels can cause anovulation. Some women with hyperprolactinemia may also notice that they have a milky discharge from their breasts. This is called galactorrhea. Patients with pituitary tumors have very high levels - typically more than 100 ng/ml.

A high prolactin level could sometimes just be because of stress - and even the stress of doing a venipuncture for drawing a blood sample can cause an artificial elevation in your prolactin levels. This means that if your levels are high, they should be re-checked, to reconfirm this diagnosis, before proceeding further.

A marginal elevation of your prolactin level is unlikely to be of any clinical importance, so don't worry too much about this. Unfortunately, we find that some doctors are so focussed on treating high prolactin levels that they suspend further testing or treatment if they find the levels are high. This is not sensible. The infertility workup should be completed.

It's also common for women with PCOD to have mildly elevated prolactin levels.

High prolactin levels in men

Men can also have high prolactin levels. Typically, these men have azoospermia, decreased libido, and erectile dysfunction. While this is not common, if diagnosed properly, it can be very effectively treated with medications!


If the level is persistently high, your doctor will have to determine what the cause for this is.

There are many possible reasons, and these include:

Prolactinoma, which is a small tumor on your pituitary gland. This tumor secretes excess prolactin into your body. They are usually very small and are called microadenomas. Large tumors are called macroadenomas and can cause headaches and visual difficulties. They can be diagnosed with MRI scanning. They can be safely treated with medical therapy with bromocriptine or cabergoline, which causes them to shrink very quickly.

Prescription Drugs
Prescription drugs can cause excess secretion of prolactin. Some anti-depressants, painkillers, and opiates block dopamine, preventing prolactin secretion from being inhibited. This can cause your prolactin levels to rise.

Other causes include Hypothyroidism and PCOS - polycystic ovarian disease. In many cases, we cannot find a cause.

How is a high prolactin level treated?

If you do have a high prolactin level, the good news is that this is treatment is very effective. Marginal elevations are usually of no clinical importance and can be ignored. If the problem is because of hypothyroidism or PCOD, then this needs to be corrected. If it's drug-induced, then stopping the drugs will solve the problem.

High prolactin levels are best treated with medical therapy. There are two very effective drugs for this - bromocriptine; and cabergoline.

Bromocriptine a drug that is used specifically to treat women with hyperprolactinemia. Bromocriptine lowers prolactin levels to normal and allows the ovary to get back to normal.

Side effects: The drug often causes nausea and dizziness during the first few days of treatment but the chances of these symptoms occurring can be reduced by starting the drug at a very low dose and gradually building up to a maintenance dose of 2 or 3 tablets daily.

Dose: A 2.5 mg tablet is available; and the starting dose is usually 2.5 mg to 5 mg daily - taken at bedtime. After starting bromocriptine, prolactin levels can be tested (after at least one week of medication) to confirm that they have been brought down to normal. If the levels are still elevated, the dose will need to be increased. Once normal prolactin levels have been achieved (and some women need as much as 4 to 6 tablets a day to achieve this) this is then the maintenance dose. Once your prolactin blood level is within the normal range, your periods should become more regular and you should start ovulating normally again. Remember that bromocriptine only suppresses an elevated prolactin level while you are taking it - it does not cure the problem. This is why the tablets must be taken daily until a pregnancy occurs, after which they should be stopped. This is expensive medication - and some pharmaceutical companies may provide it at reduced rates if your doctor requests them to do so on your behalf.

Some women cannot tolerate bromocriptine. For these women, an alternative option is a cabergoline, which is as effective in reducing high prolactin levels and has fewer side effects.


is frequently used as a second-line agent in the management of prolactinomas when bromocriptine is ineffective or is poorly tolerated.

This is available as a 0.5 mg tablet. The dose is usually 1 tablet per week. This can be increased as needed until the prolactin level becomes normal.

Check your own prolactin levels

If you live in the USA, the good news is that you can now check your prolactin levels yourself.

You can do this at MyMedLab!

Need help in interpreting the results?

Authored by : Dr Aniruddha Malpani, MD and reviewed by Dr Anjali Malpani.