Cabergoline and Libido

Cabergoline is often called a "libido drug," and on forums it is discussed as a means of shortening the refractory period. The editors examined where the proven medicine lies here, where the preliminary data are, and where the dangerous oversimplifications are.

Prolactin as a "brake" on sex drive

Prolactin is a hormone that naturally rises after orgasm, during pregnancy and during breastfeeding. One of its functions is considered to be the temporary reduction of sexual interest, and in this sense it works as a physiological "brake" on sexual activity.

When prolactin is chronically elevated, this brake effectively does not release. In men, hyperprolactinemia suppresses the secretion of gonadotropin-releasing hormone, and after it LH and testosterone. The result is reduced libido, erectile dysfunction, sometimes gynecomastia and infertility. The review by Buvat (2003) stresses that reduced libido is one of the most common manifestations of hyperprolactinemia in men.

Interestingly, prolactin can suppress sexual function not only through testosterone. In some patients, testosterone replacement therapy without correcting prolactin does not fully restore libido, which points to a direct central action of the hormone on the brain mechanisms of desire.

In women, high prolactin also reduces libido - through suppression of ovarian function, a drop in estrogens and the associated dryness of the mucous membranes. Therefore complaints about sexual function in both sexes are a strong reason to check prolactin levels.

What treatment with cabergoline gives in hyperprolactinemia

In patients with confirmed hyperprolactinemia, cabergoline normalizes prolactin in most cases. As a rule, this restores testosterone levels in men and the menstrual cycle in women, and with them sex drive and sexual function. The Endocrine Society guidelines (2011) regard dopamine agonists as the basis of treatment for such conditions.

Recovery usually occurs gradually, over weeks or months. In men with macroprolactinomas in whom the tumor has damaged the normal pituitary tissue, testosterone may not return to normal even after prolactin is normalized - then the doctor considers additional hormone therapy.

Importantly, in these situations cabergoline treats the cause - the excess of prolactin - and does not "increase libido" as such. The effect on sexual function is a consequence of correcting the hormonal imbalance.

If, however, prolactin is normal but libido is reduced, the search for the cause should continue: testosterone deficiency, depression, sleep disorders, antidepressant use, vascular problems, relationship issues in the couple. Prescribing cabergoline "at random" in such cases has no justification.

The refractory period and "pro-cabergoline" myths

The popular idea that cabergoline shortens the refractory period after ejaculation has a scientific root. The group of Krüger and colleagues in 2003 studied acute manipulation of prolactin levels in healthy men and reported that lowering prolactin with cabergoline was accompanied by changes in measures of sexual drive and function, whereas raising prolactin produced the opposite effect.

These works formed the hypothesis that the release of prolactin after orgasm is involved in the mechanisms of sexual satiety. However, the studies were small, conducted under laboratory conditions, and their results did not turn into a registered indication. Cabergoline is not approved by any regulator for the treatment of sexual disorders in people with normal prolactin.

There are also isolated retrospective observations of off-label use of cabergoline for orgasmic disorders in men. However, the level of such evidence is low: without a control group it is impossible to separate the drug's effect from placebo and the natural course.

The risks of the drug, on the other hand, are quite real: nausea, dizziness, a drop in blood pressure, impaired impulse control and, with long-term use, possible fibrotic changes in the heart valves. The benefit-risk ratio for "improving sex" in a healthy person remains undefined.

When libido becomes a problem: hypersexuality

Paradoxically, the opposite problem has also been described for cabergoline - an excessive increase in sex drive. Hypersexuality is part of the spectrum of impulse-control disorders observed with dopamine agonists. It can manifest as obsessive thoughts about sex, risky behavior, conflicts in relationships.

For a person who took the drug precisely "for libido," such changes may be perceived as a desired effect, and so their danger is underestimated. In reality this is a signal of dysregulation of the reward system, which can spread to other areas as well - gambling, shopping, food.

The prescribing information for cabergoline contains warnings about these effects, and clinical guidelines recommend that doctors actively ask patients about changes in behavior. In most cases the symptoms regress after reducing the dose or discontinuing the drug under a doctor's supervision.

Therefore sexual changes on cabergoline - both a decrease and an excessive increase in drive - should be discussed with a doctor rather than corrected on one's own.

• A sharp increase in drive that interferes with ordinary life is a reason to see a doctor.
• The appearance of other compulsive forms of behavior strengthens the suspicion of an impulse-control disorder.
• Those close to a person often notice the changes earlier than the person themselves.

The context of sports pharmacology

In the milieu where anabolic steroids are used without a prescription, cabergoline is often mentioned in connection with the so-called "prolactin" side effects of 19-nortestosterone derivatives. There is little scientifically grounded data on how much these substances raise prolactin in humans and whether sexual disorders are associated with it, and most notions are based on anecdotal reports.

Reduced libido and erectile dysfunction during or after the use of anabolic steroids have a complex nature. The leading role is played by suppression of one's own hormonal system, an imbalance of testosterone and estradiol, as well as psychological factors. The Endocrine Society review on the consequences of using doping drugs (Pope et al., 2014) describes these mechanisms in detail.

In such a situation, taking cabergoline on one's own masks the problem instead of solving it and adds new risks. The editors deliberately do not provide schemes for its use "on a cycle" and advise people with sexual complaints to undergo a full examination with an endocrinologist or andrologist.

The diagnostic minimum usually includes total testosterone, LH, FSH, estradiol, prolactin and TSH. Only with confirmed hyperprolactinemia and an established cause is treatment with a dopamine agonist discussed.

Editorial conclusions

Elevated prolactin is a proven cause of reduced libido, and in such patients cabergoline helps restore sexual function by eliminating the root cause.

The data on shortening the refractory period and "enhancing" sexuality in people with normal prolactin are preliminary, and the drug is not registered for this.

Dopamine agonists can cause hypersexuality and other impulse-control disorders, so any sharp changes in drive require a doctor's attention.

Our articles "Cabergoline and Mood," "Exemestane and Libido" and "Tests When Using Cabergoline" will help continue the topic.

References

1. Buvat J. Hyperprolactinemia and sexual function in men: a short review. Int J Impot Res. 2003;15(5):373–377.
2. Krüger TH, Haake P, Haverkamp J, et al. Effects of acute prolactin manipulation on sexual drive and function in males. J Endocrinol. 2003;179(3):357–365.
3. 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.
4. Weintraub D, Koester J, Potenza MN, et al. Impulse control disorders in Parkinson disease: a cross-sectional study of 3090 patients. Arch Neurol. 2010;67(5):589–595.
5. Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.
6. Pfizer. Dostinex (cabergoline tablets): prescribing information. U.S. Food and Drug Administration.