The underlying theory of blood type diets is that people with different blood types digest lectins differently, and that if people eat food that is not compatible with their blood type, they will experience many health problems.
Leptin is a potent stimulator of the immune system. Leptin receptors on monocytes cause the release intracellularly of STAT3 which cause the monocytes to release IL-6, IL-12 and TNF alpha. The IL-6 goes to the liver and increases production of CRP.
CRH is produced in the hypothalamus of the brain and causes the pituitary gland to produce another hormone called ACTH. The hormone ACTH then acts on the adrenal glands causing them to produce the hormone cortisol. Unfortunately, CRH levels are unable to be measured in simple blood samples. However, substances like cortisol and leptin can provide information as to the activity of the hypothalamus. The hormone leptin is associated with the regulation of body weight and the normal maintenance of bodily functions (homeostasis). It is found in fat cell (adipocyes) and communicates the nutritional status of the body to the brain (central nervous system).