Progesterone vs Progestin

Progesterone and progestin sound almost identical, and they are often used loosely as if they mean the same thing. In fact, progesterone is a specific hormone the body makes, while progestin is a broad term for laboratory-made compounds designed to act like it. This page compares the two for general understanding.

What progesterone is

Progesterone is a steroid hormone produced naturally in the body, mainly by the corpus luteum — the structure left in the ovary after ovulation — and by the placenta during pregnancy. Its central job is to prepare and stabilize the lining of the uterus after estrogen has built it up earlier in the menstrual cycle. If pregnancy does not occur, progesterone falls and the lining is shed. Beyond reproduction, progesterone has effects elsewhere in the body and serves as a building block for other steroid hormones. When clinicians talk about "progesterone," they usually mean this single, naturally occurring molecule.

What progestin is

Progestin is an umbrella term for a family of synthetic compounds developed to mimic the actions of progesterone. They are designed in the laboratory and are used in many forms of hormonal medication. Because each progestin is a slightly different molecule, members of the family do not all behave identically — they can differ in how strongly they act, how long they last, and what secondary effects they have. The word "progestin" therefore describes a category rather than one substance. A closely related word, "progestogen," is sometimes used as a broader label covering both natural progesterone and the synthetic progestins.

How they relate

The link between the two is one of model and copy: progesterone is the natural hormone, and progestins are engineered to reproduce its key effects, especially its action on the uterine lining. Both are described as acting on the same general target — progesterone receptors — which is why they share a family name. The differences arise because the synthetic molecules are not exact replicas. Small changes in chemical structure can change how a progestin interacts with progesterone receptors and with other receptors in the body, so the experience of one progestin is not necessarily the experience of another, nor of natural progesterone itself.

How they compare side by side

The points below summarise commonly discussed differences. They describe general distinctions, not rules, and the entries here are illustrative; how any compound behaves in a given person varies and should be discussed with a clinician.

For background on the underlying hormones, see the hormones index; for how related blood samples are collected, see the blood tests overview. Related conditions appear in the conditions index, treatment context lives in the treatments index, and you can browse more side-by-side explanations in the comparisons index.

Common points of confusion

The biggest source of confusion is the assumption that "progestin" and "progesterone" are simply two spellings of one thing. They are not. Progesterone is the body's own hormone; progestin refers to manufactured compounds intended to act like it. A second point of confusion is treating all progestins as a single substance — because the family includes several distinct molecules, statements about "the progestin" can be misleading without naming the specific compound. A third is the overlap with the broader word "progestogen," which can include both natural and synthetic forms depending on who is using it. Keeping these labels straight helps when reading medication information or comparing notes, and a clinician or pharmacist can clarify which exact compound is involved in any specific product.

When each matters

The distinction matters most when reading about hormonal medications, because the label tells you whether a discussion concerns the natural hormone or a synthetic stand-in. It also matters when comparing different products, since two items in the progestin family may not be interchangeable. For broader context on natural versus laboratory-made hormones, the comparison of cortisol vs cortisone illustrates a related theme — closely related molecules that are not identical.