20–40 mg/day of extract, continuously for several cycles.
One of the few herbal remedies with reasonable evidence for PMS.
View the study (RCT) →Some use in cycle disorders; scarce evidence.
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Chasteberry, also called vitex or agnus castus, is Vitex agnus-castus, a Mediterranean shrub whose dried fruits have been used since Greek and Roman antiquity for gynecological disorders, especially premenstrual syndrome, cyclic mastalgia, and menstrual irregularities related to the luteal phase; the name "castus" (chaste) refers to its traditional use to reduce libido in medieval monasteries, a pharmacological property related to its modulation of prolactin and the hypothalamic-pituitary axis that modern research has considerably qualified.
The identified active constituents are iridoids (agnuside, aucubin), flavonoids (casticin), and some diterpenes with activity on hypothalamic dopaminergic D2 receptors, which explains the plant's central mechanism of action: mild, selective inhibition of pituitary prolactin secretion, with the resulting normalization of the estrogen/progesterone ratio in the second phase of the menstrual cycle, a physiologically logical intervention for premenstrual disorders with a functional hyperprolactinemia component.
The indication with the best clinical evidence is moderate to severe premenstrual syndrome: several European randomized trials have shown significant improvements on standardized scales (PMTS, MMDQ) with doses of 20-40 milligrams per day of standardized extract for 3-6 menstrual cycles, with clinically relevant effect sizes and a better tolerability profile than most pharmacological alternatives.
A randomized trial published in the BMJ in 2001 with 178 women with PMS showed that 20 mg/day of extract for 3 cycles produced significant improvements in overall symptoms compared with placebo, with a relevant clinical response in more than 50 percent of patients; later studies have confirmed the efficacy and have positioned chasteberry as a reasonable first-line option in moderate PMS before resorting to SSRIs or hormonal contraceptives.
In cyclic mastalgia (premenstrual breast pain related to functional hyperprolactinemia), several trials have shown significant reductions in breast pain and tenderness with supplementation for 2-3 cycles, a specific indication with solid clinical support and a tolerability profile more favorable than that of pharmacological therapy with bromocriptine or danazol.
In oligomenorrhea, short cycles, intermenstrual spotting, and other manifestations of functional luteal insufficiency, chasteberry has shown improvements in cycle regularity and luteal phase length in small studies; although the evidence is weaker than for PMS, the physiological logic of the mechanism (dopaminergic modulation of prolactin with normalization of the axis) justifies its use in selected patients.
In mild to moderate functional hyperprolactinemia (not caused by a pituitary adenoma but by chronic stress, subclinical hypothyroidism, or other functional causes), chasteberry can normalize levels and restore regular ovulation in women who have difficulty conceiving; in hyperprolactinemia caused by a prolactinoma or an organic cause, pharmacological dopamine agonists (cabergoline, bromocriptine) are clearly superior and chasteberry is not an alternative.
The doses studied range from 20 to 40 milligrams per day of standardized dry extract (Ze 440, Agnolyt, and other European formulations with good clinical documentation), taken in the morning with or without food; the effect on premenstrual symptoms typically appears from the second or third cycle and requires at least 3-6 cycles for a full assessment; the effect lasts only as long as use continues.
Generally well tolerated; the most frequent adverse effects are mild headache, digestive discomfort, and occasionally itching or skin rash; the most important contraindications are pregnancy (the effect on prolactin and estrogen receptors may interfere with gestational development), breastfeeding (reduced milk production due to prolactin inhibition), concurrent use of hormonal contraceptives (theoretical interference with the contraceptive effect), and hormone-dependent tumors (breast, endometrium, ovary); people with Parkinson's disease or those taking dopamine agonists or antagonists should use it only under medical supervision because of the expected pharmacodynamic interaction.
Information, not medical advice. Scientific evidence reflects the quality of the studies.