Cooperative Estrogen Replacement Therapy (CERT)

By RRM Academy Reviewed by Dr. Naomi Whittaker, MD, Board-Certified OBGYN, MIGS, NFPMC, FCI Updated May 7, 2026

Cooperative Estrogen Replacement Therapy (CERT) is a cycle-timed estradiol supplementation protocol used in NaProTECHNOLOGY to correct deficient estrogen output in specific subtypes of luteal phase deficiency and impaired follicular development.⁷⁸

CERT is the sister protocol to Cooperative Progesterone Replacement Therapy (CPRT). It addresses Type V LPD, defined by isolated luteal estradiol deficit, and Type B or C follicular phase function grades where estradiol production is suboptimal across the pre-ovulatory phase. Like CPRT, it is not continuous. Dosing tracks the cycle; it does not override it.

CERT exclusively uses isomolecular 17β-estradiol. Ethinyl estradiol, the synthetic estrin found in oral contraceptives, is a heteromolecular artimone and is not used in NaPro hormone protocols. Cycle-timed estradiol targeted to a confirmed ovulatory window and a documented deficiency is the clinical standard in NaPro practice.

This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.