Abnormal Vaginal Bleeding Following Pharmacist Prescribing of Metformin Leads to the Detection of Complex Endometrial Hyperplasia

Objective: To describe a case where pharmacist prescribing of metformin therapy resulted in unexplained vaginal bleeding in a patient later diagnosed with complex endometrial hyperplasia. Case Summary: A 57-year-old woman with diagnoses of hypertension and dyslipidemia was assessed by a pharmacist with prescribing authorization for hypertension management. Cardiovascular risk assessment performed by the pharmacist resulted in the detection of metabolic syndrome confirmed by the patient’s physician. The pharmacist prescribed metformin 500 mg twice daily for prediabetes and metabolic syndrome, resulting in vaginal bleeding 1 week following initiation of therapy. Bleeding stopped following discontinuation of metformin, and recurred on retrial. The symptoms were dose dependent as bleeding did not occur at a dose of 500 mg once daily, but recurred at a total dose of 1000 mg/d. The patient was referred for physical examination and endometrial ultrasound and sampling, and was found to have complex endometrial hyperplasia. Discussion: Metformin is widely used for the treatment of polycystic ovary syndrome as it improves ovulation and menstrual cycle regularity. In this case, the patient was not known to have polycystic ovary syndrome but was instead provided metformin for metabolic syndrome and hyperinsulinemia. It is believed that metformin’s endocrine effects resulted in the sloughing of this hyperplastic tissue, prompting the pharmacist to refer the patient for medical assessment. This case is unique as it is the first of our knowledge to report a scenario where pharmacist prescribing resulted in facilitated detection of a previously undetected disease, highlighting that an expanded scope of practice for pharmacists can facilitate disease diagnosis when collaboration occurs among health professionals. Conclusions: Female patients initiated on metformin therapy should be aware that any changes to their menstrual cycle following metformin may indicate endometrial disease. Additionally, pharmacist prescribing for chronic disease management, when practiced collaboratively with the patient and their physician, can facilitate disease detection through effective referral and follow-up.