Agnuside is an iridoid glycoside and one of the main active constituents found in the fruit of Vitex agnus-castus (chasteberry), an herbal remedy traditionally used for various gynecological conditions, including premenstrual syndrome (PMS). PMS Type H is characterized by symptoms related to "hyperhydration," such as bloating, breast tenderness, and water retention. The use of chasteberry extracts, which contain agnuside, for PMS—particularly with symptoms of breast tenderness and swelling—has some support in the scientific literature.

Clinical studies and meta-analyses have shown that Vitex agnus-castus extracts can reduce several PMS symptoms, notably mastalgia (breast pain/tenderness) and edema, both of which are prominent in PMS Type H. The proposed mechanism involves dopaminergic activity, which inhibits prolactin release from the pituitary gland; elevated prolactin is associated with breast tenderness and fluid retention. Agnuside is thought to contribute to these effects, although it is not always isolated in clinical studies—the benefit is generally attributed to the whole extract.

While most studies use standardized extracts of chasteberry rather than agnuside alone, agnuside is used as a marker compound for extract quality and presumed activity. Evidence from randomized controlled trials is moderate in quality and supports the use of chasteberry extracts for PMS symptoms, especially Type H. Thus, the use of agnuside-containing extracts for PMS Type H is scientifically supported, though the evidence is not robust enough for the highest rating.