Chasteberry (Vitex Agnus-Castus)

Chasteberry acts on dopamine D2 receptors in the pituitary gland to inhibit prolactin secretion. Elevated prolactin suppresses progesterone production in the luteal phase. By reducing prolactin, chasteberry indirectly supports progesterone production — addressing one of the most common causes of luteal phase deficiency and PMS. It also has mild opioid receptor activity that contributes to mood stabilization.

The foundational ingredient for progesterone support and PMS management. Most women with estrogen dominance have relative progesterone deficiency — chasteberry addresses this by supporting the body's own progesterone production rather than providing exogenous hormones.

Multiple RCTs confirm efficacy for PMS and PMDD. A 2001 BMJ study showed chasteberry was as effective as fluoxetine (Prozac) for PMDD with fewer side effects. A 2017 meta-analysis confirmed significant reduction in PMS symptoms across multiple studies.

20–40mg daily, taken in the morning. Effects on cycle regulation typically require 3 menstrual cycles (3 months) of consistent use. Best taken continuously rather than cyclically for PMS management.