The pancreas produces vital hormones, but it is also regulated by hormones produced elsewhere in the body. Understanding how those hormones work is a little bit obscure, but vitally important if you are concerned about cancer.
Several years ago Dr. Guillermo Robles-Diaz and Dr. Andres Duarte-Rojo of the National Institute of Medical Sciences and Nutrition Salvador Zubirán in Mexico City explained the role of sex hormones in pancreatic tissue. Just like many other organs in the body, the pancreas grows in response to sex hormones, but different sex hormones affect different parts of the organ.
1. The insulin-producing beta cells become more active in response to estrogen. This means that if you have a really rare kind of usually (but not always) non-cancerous tumor known as an insulinoma, then estrogen replacement therapy can make the tumor worse. You'd know this by your blood sugar levels running really low.
This phenomenon is more important for diabetics. Higher estrogen levels are associated with lower rates of diabetes. This fact explains why so many people who develop diabetes often gain weight first--it's actually a self-defense mechanism. Fat cells make estrogen. The more estrogen fat cells make, the more insulin a sick pancreas can make. As hard as it may be to believe, putting on fat doesn't cause diabetes, diabetes causes fat mass, and the common link is insulin. Fortunately, the cells that work overtime to make are very seldom the part of the organ that becomes cancerous.
2. These same insulin-making cells become less active in response to progesterone. Women's bodies make tremendous amounts of progesterone during pregnancy. The production of progesterone may account for gestational diabetes--which usually goes away after the baby is born.
Women who use high-progesterone birth control pills may be at higher risk of type 2 diabetes. They may also be at higher risk of insulinoma, which, ironically, will produce the exact opposite of the high blood sugar symptoms some women have during pregnancy. The risk for cancer in other parts of the pancreas, however, goes down when women use or have used birth control pills containing estrogen. The more children women have had, the less likely they are to have this pancreatic cancer later in life.
3. When the rest of the pancreas develops cancer, these cancerous parts become very sensitive to testosterone. They work overtime to convert the male sex hormone into its active form.
What's the message to take away from the science? Here are three main possibilities:
1. Since belly fat turns testosterone into estrogen, it's a risk factor for insulinoma. If you have insulinoma, you won't have diabetes. Oddly enough, a little extra fat (as an energy source when you can't eat) protects against death in pancreatic cancer, although it can make the surgeon's job a lot more difficult.
2. Any kind of sex hormone replacement or birth control for women that's high in progesterone raises the risk of diabetes and lowers the risk of pancreatic cancer, and
3. If you are concerned about preventing or treating pancreatic cancer, use testosterone replacement with extreme caution. More of the injected form actually stays in the system as testosterone. The patches tend to produce estrogen because they are absorbed through the fat that lies beneath the skin.
Alabraba EB, Taniere P, Reynolds GM, Stewart PM, Wigmore SJ, Bramhall SR. Expression and functional consequences of oestrogen and progesterone receptors in human insulinomas. Endocr Relat Cancer. 2007 Dec;14(4):1081-8.