Progestin" is a general term for a substance that causes some or all of the biologic effects of progesterone. The term "progestin" is sometimes used to refer to the progesterone made in the laboratory that is in oral contraceptives and hormone replacement therapy. However, all progesterone and progestin products are made in the laboratory. The term "natural progesterone" is really a misnomer. "Natural progesterones," including the prescription products Crinone and Prometrium, are made from a chemical called diosgenin that is isolated from wild yam or soy. In the laboratory, this constituent is converted to pregnenolone and then to progesterone. The human body is not able to make progesterone from diosgenin, so eating wild yam or soy will not boost your progesterone levels.
Over-the-counter (OTC) progesterone products may not contain progesterone concentrations as labeled. According to a British report, two-ounce jars of Progest cream used in a clinical trial contained 100 mg progesterone per ounce rather than the 465 mg claimed by the manufacturer.