Progesterone is the precursor to many hormones, including testosterone, the sex hormone that emphasizes male characteristics, and estrogen, the sex hormone that emphasizes female characteristics. Progesterone plays an important role in regulating blood sugar, building bone mass, regulating brain activity, developing intelligence and body functions. It also contributes to the process that converts fat into energy, regulates thyroid hormone production and can help reboot libido. Aside from this, progesterone is a natural antidepressant, an aid to normalizing blood clotting, a contributor to initiating sleep and a natural diuretic along with many other vital functions.
Low Progesterone Levels
As men age, testosterone levels decline and estrogen levels start to rise. Progesterone levels in men drop sharply as estrogen levels climb, causing symptoms such as low libido, hair loss, weight gain, fatigue, depression, gynecomastia -- enlarged breasts -- erectile dysfunction, impotence, bone loss and muscle loss. Aside from this, men who have low levels of progesterone have a greater risk of developing serious illnesses such as osteoporosis, arthritis, prostatitis and prostate cancer.
Progesterone and Cancer
Progesterone helps prevent prostate disease by preventing testosterone from being converted into dihydrotestosterone, or DHT, which, when produced in excessive amounts, can cause damage and even cancer, according to the Natural Progesterone Information Service. Another way progesterone helps reduce the risk of cancer is by suppressing the growth-promoting effects of estrogen and testosterone on cells that have outlasted their natural lifespan. Cells that live longer than they should due to the influence of estrogen and testosterone produce too many daughter cells that could develop mutations that give rise to cancer.
Estrogen and Heart Disease
There is some evidence that men who have just the right amount of estrogen in their bodies may have better chances of surviving chronic heart failure, according to a Polish study published in the May 2009 issue of the "Journal of the American Medical Association." Men with very low estrogen were found to have a 44.6 percent survival rate while those with slightly higher estrogen levels had a survival rate of 65.8 percent. Men with moderate levels of estrogen had the highest survival rate at 82.4 percent while those with elevated levels had a lower survival rate at 79.0 percent. The men with the highest estrogen levels had a 63.6 percent survival rate. More research is needed to determine exactly what kind of relationship estrogen levels have with the chances of surviving chronic heart disease.
Estrogen and Osteoporosis
There is also some evidence that estrogen plays a role in how much bone density a man has, a study in the April 4, 2007 issue of "Calcified Tissue International" reports. Several enzymes in the liver convert standard estrogen into estrogen metabolites, some of which are active while others are inactive. The more active estrogen metabolites a man has in his body, the denser his bone mineral density tends to be. While testosterone seems to be responsible for the how large male bones become and how thick their outer layers become, it is estrogen that is the key hormone for maintaining peak bone mineral mass in men.