Prolactin-Secreting Microadenoma Masked By A Herbal Product, Vitex Agnus-Castus

ABSTRACT Objective: This case involves the presentation of a pituitary microadenoma that was confounded by the patient's use of an herbal product which led to a delay in diagnosis. Methods: Clinical presentation, biochemical features, imaging, and impact of an herbal product, Vitex agnus-castus (VAC), on the presentation of a case of pituitary microadenoma. Results: We present a case of pituitary microadenoma in a 28-year-old female who had initially presented with oligomenorrhea, galactorrhea, and mild elevation of prolactin (PRL) levels. Evaluation in the endocrinology office revealed a complete resolution of symptoms and normalization of labs indicating only a transient elevation of PRL levels. A detailed history, which included the use of over the counter medications (VAC), revealed a potential contributor to the patient's symptomatic improvement in the interim. Ceasing supplementation with the herb led to the recurrence of patient symptoms and a rebound elevation of PRL. A complete workup showed radiological evidence of a pituitary microadenoma on a magnetic resonance imaging scan with contrast. Conclusion: This case highlights the importance of a complete medication history, including herbal products and over the counter medications, and its importance in ruling out a diagnosis. Repeat testing after stopping the herbal product unmasked the microadenoma that would have been missed otherwise. Abbreviations: PMS = premenstrual syndrome; PRL = prolactin; VAC = Vitex agnus-castus