Isomolecular Hormones (IMH)

Isomolecular hormones (IMH) are hormone medicines with the same molecular structure as the hormones the body makes. Progesterone and estradiol are two examples. After ovulation, the corpus luteum makes most of the body's progesterone. It also makes estradiol. The term was developed by Dr. Thomas W. Hilgers as part of NaProTechnology. It sets these medicines apart from heteromolecular ones, which use a molecule that differs from the body's own hormone.¹

The reason for using them is simple. A hormone molecule that matches the body's own should fit the same receptors and act the same way. It supports normal function instead of imitating it. Hilgers and colleagues documented the use and safety of isomolecular progesterone in pregnancy support. They set it apart from synthetic progestins and other heteromolecular compounds.¹

In NaProTechnology, isomolecular hormones are the basis for both CPRT and CERT. That choice follows a core design principle: work with the body's own physiology rather than swap in a drug that acts differently. Synthetic progestins and conjugated equine estrogens have a different structure. That structure changes how they bind receptors and what they do in the body.²

Isomolecular progesterone comes in several forms. The treating clinician chooses the form, dose, and route. The choice rests on the patient's history, cycle chart, and lab results. The word "isomolecular" comes from NaProTechnology. It may not carry the same meaning outside that setting.