What is Progesterone?

• Oldest known sex hormone. 
• Present in every human regardless of age. 
• Produced by the ovaries and adrenal gland. 
• Secreted by corpus luteum. 
• Has receptors in nearly every cell in the body. 
• Acts on uterus, kidneys, brain, smooth muscle, breasts, bones, and cellular membranes. 
• Metabolized to other active hormones. 
• What are some of the functions and roles of progesterone in the body?
• Counteracts estrogen's tendency to induce excess growth in the endometrial lining of the uterus. 
• Builds new bone tissue, leading to increased bone mass and density. 
• Necessary for maintenance of pregnancy. 
• Decreases uterine contractions. 
• Prepares and maintains uterine lining for implantation of fertilized egg 
• Prepares breasts for lactation. 
• Assists in raising HDL-cholesterol levels (if combined with estrogen therapy) and ultimately reduces risk of heart disease. 
• Synthetic progesterone (progestin) has an overall negative effect on HDL-cholesterol levels because it vasocontricts. 

What is the difference between "progestin" and "progesterone?"

The main difference is in the derivative. Progestin’s are synthetic (i.e. man-made) molecules developed to act like natural progesterone.  Natural progesterone is a molecule that is plant derived and is bio-equivalent to the hormone produced in our bodies.  Progestin’s do not have as broad a spectrum of activity as natural progesterone, and have a wide range of side effects.  Whereas progesterone may cause some mild to moderate drowsiness, progestin’s can cause:

• breast tenderness 
• acne 
• depression 
• vision changes 
• bloating 
• migraine headaches 
• thrombosis 
• decreased glucose tolerance 
• gastric regurgitation