ENDOCRINOLOGY

Endocrinology



Endocrinology

QUESTION 1:

Hormones never initiate biological processes, will not put an end, only modify the speed of a metabolic pathway. For this there are 3 possibilities or ways:

Increasing the concentration of the first substrate, such as insulin, which stimulates glucose uptake.

Increasing the concentration of the enzyme, which involves synthesizing more enzyme, which are steroid hormones.

Altering the activity of the enzyme without changing its concentration. Enzymes can be in an inactive state and active, so you want to see the relationship between them. (Katila , 1993)

Every time a hormone binds to its receptor is hormone receptor forms a complex with the following characteristics:

The affinity is very great between the ligand and its receptor (not further apart).

Specificity, is highly specific for each ligand is a specific receptor, may have, yes, more than one type of receptor for each ligand.

All cells are immersed in the LEC, whose composition is very variable. The cells are not passive entities but respond to environmental conditions. For example, all cells (with exceptions) have surface receptors for insulin, people with diabetes lack insulin, so that the cell placed over the membrane receptors (up regulation) by increasing its sensitivity to insulin(Arlt , 2004). Conversely, there is an obesity that is caused by excess insulin, where the cell responds with a "down regulation" by decreasing the number of receptors or changing their affinity.

The up-regulation and down (up and down regulation) may be

Homologous: when, for example, insulin affects its receptors.

Heterologous: when other ligands may affect the number of insulin receptors.

When the cell has all its receptors complexed, recycle it. The process is as follows: the cell internalizes the receptors involved in a "basket" of clathrin, forming a membrane invaginations (ACTE pits) and passing into the cell in a vesicle and then separates the clathrin (joins a receptosoma), changing the pH, losing affinity, and the receptor is recycled to the membrane, the ligands end in a lysosome. Sometimes there is no response to the hormone receptor complex formation. Desensitization of complex HR (hormone receptor)

QUESTION 2:

Polypeptide hormones: up 99% of the messenger molecules, is characterized by being soluble in water and because they penetrate the target cell, it interacts with receptors on the surface.

Steroid hormones, all derived from cholesterol, has no polar groups, and is insoluble in water, are classified into 3 families:

C-21 steroids: cholesterol with 21 carbon atoms is the precursor of these hormones: cortisol, aldosterone, progesterone.

C-19 steroids: are androgens (male sex hormones).

C-18 steroids: are estrogen (female sex hormones). (Pawelec, 2004)

Because they are lipid soluble penetrate all cells. The adrenal cortex and gonads produce steroid. Some cells have receptors, some not.

Hormones derived from amino acids

Solubility in Water: catecholamines: adrenaline, noradrenaline, dopamine. Not penetrate the effector cell. Insoluble in water: thyroxine, enter the effector cell.

Phospholipid-derived hormones

Eicosanoids: are produced by every cell in the body. Recall that a is a glycerol phospholipid that binds 1, 2 or 3 fatty acids (mono, di-or triacylglycerol), instead of a fatty acid may have a phosphate group (phosphatidic acid), which in turn can react for example, ...