Hormones Controlling Growth Development and Metabolism

The major control of growth is carried out by so-matotropin (STH) from the anterior pituitary. STH does not act directly, however. Cells in the liver respond to STH to produce somatomedin, which stimulates bone growth and muscle production. Prolactin, a protein similar to STH, stimulates breast development in female mammals. In an interesting case of hormone evolution, thyroid hormone stimulates amphibian metamorphosis (tadpole to frog transition); however, in warmblooded vertebrates, this same hormone has evolved to stimulate metabolism for the purpose of heat production in birds and mammals. Several hormones stimulate metabolism for different reasons. Epinephrine (adrenaline), in addition to elevating blood pressure, mobilizes glucose from glycogen, in response to stress. Steroid hormones, also produced in the adrenal glands, stimulate the production of glucose from noncarbohydrate molecules (gluconeogenesis). The stimulus for this is prolonged stress, for example, starvation. These glucocorticoids, such as cortisol and corticosterone, evolved early and are very important in combating stresses resulting from migration among birds and even fish. The pancreatic hormones insulin and glucagon also effect energy metabolism. These two proteins regulate blood sugar, fat, and protein levels. After eating, insulin stimulates transport of these molecules into liver, fat, and muscle cells and then stimulates the incorporation of the simple molecules, such as glucose, amino acids, and fatty acids, into larger storage molecules, such as glycogen, protein, and fats. Glucagon has opposite actions. After a prolonged period without food intake, glucagon stimulates breakdown of complex molecules, such as glyco-gen and fats, into simple molecules, which are released into the blood and made available to metabolizing cells. These two hormones act independently of the pituitary and respond directly to blood-borne signals such as glucose concentration. This regulation ensures a steady delivery of nutrients to metabolizing cells in animals who only eat intermittently.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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