Tribulus terrestris for treatment of sexual dysfunction in women: randomized double-blind placebo - controlled study.

The short version

This randomized, double-blind, placebo-controlled trial of 67 randomized women (60 analyzed) explored whether an extract of Tribulus terrestris, a low-growing plant also called puncture vine or bindii, affects sexual desire in women of childbearing age. The condition studied, hypoactive sexual desire disorder (HSDD), is a persistent lack of sexual thoughts and desire that causes personal distress, and the authors cite a prevalence of about 1 in 10 adult women in the USA and 30% in Iran. No drug is approved by the US Food and Drug Administration for it. In Iranian Traditional Medicine, texts including Avicenna's Canon of Medicine describe Tribulus as a remedy that boosts libido. The women, all married and living with a partner, were recruited at two medical centers in Tehran Province, Iran, between June 2012 and July 2013, with an average age of 36 years. After random assignment in a 1:1 ratio, one group took a syrup made from an ethanol extract of Tribulus leaves, 7.5 ml twice a day for four weeks, and the other took a look-alike sucrose syrup. Sexual function was scored with the Female Sexual Function Index (FSFI), a 19-item questionnaire covering desire, arousal, lubrication, orgasm, satisfaction and pain, completed at baseline and four weeks after treatment ended. Desire, the primary outcome, rose from 3.06 to 3.90 points in the Tribulus group but only from 2.66 to 2.86 with placebo, an adjusted difference of 0.71 points (95% CI 0.41 to 1.01, p < 0.001, meaning the gain was unlikely to be chance). Several other domains also favored Tribulus: satisfaction by 1.10 points, orgasm by 0.85, arousal by 0.75, lubrication by 0.50 and pain by 0.37 (p-values between < 0.001 and 0.041). The total FSFI score improved from 21.25 to 26.80 with Tribulus versus 20.89 to 22.41 with placebo (p = 0.040 in the results text, although the abstract gives p < 0.001). Only one participant reported a side effect, a mild (grade 1) abdominal cramp. Dropouts cited the very sweet taste and anxiety about taking an investigational drug. The authors interpret the results as supporting the traditional libido-boosting reputation of Tribulus and call for larger studies. Limitations include the small sample, only four weeks of treatment with a single follow-up, one country, and a cultural setting in which women may be reserved about reporting sexual matters. The dose is stated inconsistently between the abstract and the methods, and menopausal women were excluded, so the findings do not extend to them. The mechanism was not tested; the authors only propose a possible link to follicle-stimulating and luteinizing hormones.

Key findings

• A trial in Iran randomly assigned 67 women with hypoactive sexual desire disorder (a lasting lack of sexual desire that causes distress) to a Tribulus terrestris plant extract syrup or a placebo syrup for four weeks, and 60 completed it.
• Desire scores on the Female Sexual Function Index (a 19-question self-report questionnaire) rose from 3.06 to 3.90 with Tribulus and from 2.66 to 2.86 with placebo, an adjusted difference of 0.71 points (p < 0.001).
• Arousal, lubrication, orgasm, satisfaction and pain scores also favored Tribulus (p-values from < 0.001 to 0.041), although the paper's abstract, text and table report some of these statistics inconsistently.
• Only one participant reported a side effect, a mild abdominal cramp, so the trial found no safety signal, though it was small and lasted only four weeks.
• The authors conclude that Tribulus terrestris may safely and effectively improve desire and call for larger studies; the trial excluded menopausal women and was run in a single country.

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