Cabergoline vs Vitamin B6 for Prolactin: What to Choose and for Whom

A person sees elevated prolactin on a test form and looks for something to ‘knock it down’: some think of cabergoline, some of vitamin B6. But the right answer depends on the cause, and in some cases treatment is not needed at all. The editorial team examines for whom and in which situations doctors consider each option.

First — find out whether prolactin is really elevated

Prolactin is one of the most ‘sensitive’ hormones. Its level rises after stress, intense physical exertion, sleep, sexual intercourse, breast stimulation, even from a painful blood draw. Therefore a single moderately elevated result is not yet a diagnosis of hyperprolactinemia.

The Endocrine Society guidelines (Melmed et al., 2011) consider one correctly performed test sufficient, but in the case of a doubtful moderate elevation it is advisable to repeat the test under calm conditions. It is also important to rule out macroprolactinemia — a state in which a ‘big’ low-activity complex of prolactin with antibodies circulates in the blood. Such people usually have no symptoms and do not require treatment.

Next the doctor looks for the cause: rules out pregnancy, assesses thyroid and kidney function, reviews all medications and supplements. If there is no obvious cause and prolactin is persistently elevated, an MRI of the pituitary is ordered to look for a prolactinoma.

Only after going through this path can one speak of a choice of treatment. Skipping the diagnostic work-up is the most frequent mistake, which leads to the late detection of pituitary tumors.

For whom cabergoline is indicated

Cabergoline is the first-line drug for patients with a symptomatic prolactinoma: a pituitary microadenoma or macroadenoma. It lowers prolactin and reduces the tumor size in most cases, which can eliminate even visual disturbances caused by a macroadenoma pressing on the optic chiasm.

The second group is idiopathic hyperprolactinemia with clinical manifestations: menstrual cycle disturbances, infertility, galactorrhea, decreased libido or erectile dysfunction in men. If there are no symptoms and prolactin is moderately elevated, the doctor may choose observation.

The third situation is women who are planning a pregnancy and have hyperprolactinemic infertility. Cabergoline restores ovulation, and after pregnancy occurs treatment is usually stopped, except in special cases of macroadenomas, which the endocrinologist decides.

Cabergoline is also registered for stopping lactation for medical reasons. For treating Parkinson's disease, however, it is rarely used today because of the risk of valvular pathology at high doses (Schade et al., 2007).

When it is not prolactin that needs treating but the cause

Quite often elevated prolactin is only a ‘warning light’. In primary hypothyroidism high thyrotropin-releasing hormone stimulates the lactotrophs, and prolactin normalizes after correcting thyroid function. Cabergoline is not needed in such a situation.

Drug-induced hyperprolactinemia is one of the most frequent causes. It is caused by antipsychotics, some antidepressants, prokinetics (metoclopramide, domperidone). The decision here is made by the doctor who prescribed the main therapy: sometimes it is possible to replace the drug, and unsupervised discontinuation of psychiatric medications is unacceptable. Dopamine agonists in patients with psychoses can worsen the condition, so they are used only cautiously.

In people who use anabolic steroids or other hormonal preparations, fluctuations in prolactin are also possible. But here too prolactin is only one of the indicators; unsupervised ‘lowering’ of it with cabergoline without assessing the overall picture does not solve the problem and adds risks.

Kidney failure, cirrhosis, chest injury, and shingles can also raise prolactin. Each of these causes is treated separately, and cabergoline is not a universal answer.

For whom vitamin B6 is appropriate

Vitamin B6 is an important nutrient, and taking it is appropriate in a confirmed deficiency or risk of deficiency: in people with alcohol dependence, in some chronic kidney and intestinal diseases, when taking certain medications (for example, isoniazid), and also with a very limited diet. Such a correction can be beneficial for general health, but it is not a treatment for hyperprolactinemia.

For most adults the need for B6 is covered by an ordinary diet. Good sources are poultry, fish, potatoes, bananas, chickpeas, and whole-grain products. Recommended intake norms are given below according to the data of the US Institute of Medicine.

• Adults 19–50 years: 1.3 mg per day.
• Men from 51 years: 1.7 mg per day.
• Women from 51 years: 1.5 mg per day.
• Pregnancy and breastfeeding: the norms are somewhat higher.

If a person takes B6 as part of multivitamins, sports complexes or ZMA-like products, it is worth summing up the dose from all sources. Tolerable upper intake levels differ in different regions, and the EFSA in 2023 set a substantially lower upper level for adults than the one in force in the USA. Prolonged intake of large doses is associated with a risk of sensory neuropathy (Schaumburg et al., 1983).

Therefore the editorial team does not recommend taking high doses of B6 ‘for prolactin’. If there is a wish to support the diet with B vitamins, doses close to the daily norm, or a full-fledged diet, are sufficient.

Typical self-medication mistakes

The first mistake is to treat the number, not the person. A slight rise in prolactin without symptoms after stress or a workout does not require any medications, only a repeat test under the right conditions.

The second is taking cabergoline without a prescription and monitoring. Dopamine agonists can cause a sharp drop in blood pressure, nausea, impulse control disorders, and, with prolonged use of high doses, damage to the heart valves. Excessive suppression of prolactin is also not a goal: in men very low prolactin gives no advantages, and possible undesirable effects only accumulate.

The third is hope placed in vitamin B6 instead of examination. A person with a prolactinoma who takes vitamins for months loses time, while the macroadenoma may meanwhile grow and press on the optic nerves.

The fourth is taking ‘mega-doses’ of B6 from sports supplements. Numbness or tingling in the hands and feet is a signal to stop taking them immediately and consult a doctor.

Editorial conclusions

Cabergoline is needed for people with a prolactinoma or symptomatic hyperprolactinemia without another cause that can be eliminated. It is effective, but it has serious side effects and requires medical supervision.

Vitamin B6 is appropriate for correcting a deficiency and supporting normal nutrition, but it is not a means of treating elevated prolactin. Its large doses carry a risk of neuropathy.

Many people with ‘high prolactin’ on a test form need neither of these agents — it is enough to repeat the test, rule out macroprolactin and eliminate the cause, for example hypothyroidism or the effect of medications.

We also recommend reading our materials on the mechanistic differences between cabergoline and vitamin B6, on thyroid hormone tests, and on safe doses of B vitamins in sports supplements.

References

1. Melmed S, Casanueva FF, Hoffman AR, et al. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(2):273–288.
2. Webster J, Piscitelli G, Polli A, et al. A comparison of cabergoline and bromocriptine in the treatment of hyperprolactinemic amenorrhea. N Engl J Med. 1994;331(14):904–909.
3. Schade R, Andersohn F, Suissa S, Haverkamp W, Garbe E. Dopamine agonists and the risk of cardiac-valve regurgitation. N Engl J Med. 2007;356(1):29–38.
4. Schaumburg H, Kaplan J, Windebank A, et al. Sensory neuropathy from pyridoxine abuse: a new megavitamin syndrome. N Engl J Med. 1983;309(8):445–448.
5. Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
6. EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA). Scientific opinion on the tolerable upper intake level for vitamin B6. EFSA J. 2023.