Isomolecular Hormones (IMH)
Isomolecular hormones (IMH) are hormone preparations that are chemically identical to those the human body produces, including progesterone identical in molecular structure to that secreted by the corpus luteum and estradiol identical to that produced by the ovaries. The term was developed by Dr. Thomas W. Hilgers as part of NaProTechnology to distinguish these preparations from heteromolecular alternatives, hormone compounds that differ in molecular structure from endogenous hormones.1
The clinical rationale for using isomolecular hormones in NaProTechnology rests on the principle of molecular-identity matching: a preparation that is structurally identical to the hormone the body makes is expected to interact with the same receptors in the same way, supporting physiologic function rather than approximating it. Hilgers and colleagues documented the use and safety profile of isomolecular progesterone in pregnancy support, distinguishing it from synthetic progestins and other heteromolecular compounds that do not share this molecular identity.1
In the context of NaProTechnology's cooperative replacement protocols, isomolecular hormones form the pharmacological basis for both CPRT and CERT. The preference for isomolecular preparations reflects the broader NaProTechnology design principle of cooperating with the body's physiology rather than substituting a pharmacologically active analog for it. Synthetic progestins and conjugated equine estrogens, by contrast, carry structural differences that affect receptor binding and downstream effects.2
Isomolecular progesterone is available in several preparations. The treating clinician selects the formulation, dose, and route based on the patient's clinical presentation, cycle chart data, and assay findings. Isomolecular hormones are a specific category within the broader pharmacology of hormone support; the term "isomolecular" is a NaProTechnology-originating designation and may not correspond to terminology used outside this clinical framework.
Cited in this entry
- Hilgers TW, Keefe CE, Pakiz KA. The Use of Isomolecular Progesterone in the Support of Pregnancy and Fetal Safety. Issues Law Med. 2015. https://rrmacademy.org/library/the-use-of-isomolecular-progesterone-in-the-support-of-pregnancy-and-fetal-safet-rec9gz3n4iplw6vym/
- Hilgers TW. The Medical and Surgical Practice of NaProTECHNOLOGY. Pope Paul VI Institute Press; 2004. https://rrmacademy.org/library/the-medical-surgical-practice-of-naprotechnology-rectiyuppdjrktphh/
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.