Steroid hormones chemical structure

These hydrophilic (and mostly large) hormone molecules bind to receptors on the surface of "target" cells; that is, cells able to respond to the presence of the hormone. These receptors are transmembrane proteins . Binding of the hormone to its receptor initiates a sequence of intracellular signals that may

  • alter the behavior of the cell (such as by opening or closing membrane channels ) or
  • stimulate (or repress) gene expression in the nucleus by turning on (or off) the promoters and enhancers of the genes.
This is the sequence of events:
  • The hormone binds to a site on the extracellular portion of the receptor.
    • The receptors are transmembrane proteins that pass through the plasma membrane 7 times, with their N-terminal exposed at the exterior of the cell and their C-terminal projecting into the cytoplasm.
  • Binding of the hormone to the receptor
    • activates a G protein associated with the cytoplasmic C-terminal.
    • This initiates the production of a "second messenger" . The most common of these are
      • cyclic AMP , ( cAMP ) which is produced by adenylyl cyclase from ATP (shown here), and
      • inositol 1,4,5-trisphosphate ( IP 3 )
    • The second messenger, in turn, initiates a series of intracellular events (shown here as short arrows) such as
      • phosphorylation and activation of enzymes;
      • release of Ca 2+ into the cytosol from stores within the endoplasmic reticulum.
    • In the case of cAMP, these enzymatic changes activate the transcription factor CREB ( c AMP r esponse e lement b inding protein).
    • Once bound to its response element 5' TGACGTCA 3' in the promoters of genes that are able to respond to the hormone, activated CREB turns on gene transcription .
    • The cell begins to produce the appropriate gene products in response to the hormonal signal it had received at its surface.
Steroid Hormones Steroid hormones, being hydrophobic molecules, diffuse freely into all cells. However, their "target" cells contain cytoplasmic and/or nuclear proteins that serve as receptors of the hormone. The hormone binds to the receptor and the complex binds to hormone response elements — stretches of DNA within the promoters of genes responsive to the hormone. The hormone/receptor complex acts as a transcription factor turning target genes "on" (or "off").

Cortisol - Cortisol is important for maintaining blood sugar levels, maintenance of body fluids and electrolytes, and protecting the body from stress. Cortisol has anti-inflammatory action, maintains blood sugar level, blood pressure, and muscle strength.

Dehydroepiandrosterone (DHEA) - Dehydroepiandrosterone is a steroid precursor produced by the adrenal gland and converted to testosterone or the estrogens by the body's tissues. DHEA appears to facilitate improved cholesterol profiles, loss of body fat, increased muscle gain.

Many hormones and their structural and functional analogs are used as medication . The most commonly prescribed hormones are estrogens and progestogens (as methods of hormonal contraception and as HRT ), [12] thyroxine (as levothyroxine , for hypothyroidism ) and steroids (for autoimmune diseases and several respiratory disorders ). Insulin is used by many diabetics . Local preparations for use in otolaryngology often contain pharmacologic equivalents of adrenaline , while steroid and vitamin D creams are used extensively in dermatological practice.

Diabetes results from inadequate levels of insulin. Type I diabetes is characterized by inadequate levels of insulin secretion, often due to a genetic cause. Type II usually develops in adults from both genetic and environmental causes. Loss of response of targets to insulin rather than lack of insulin causes this type of diabetes. Diabetes causes impairment in the functioning of the eyes, circulatory system, nervous system, and failure of the kidneys. Diabetes is the second leading cause of blindness in the US. Treatments involve daily injections of insulin, monitoring of blood glucose levels and a controlled diet.

Steroid hormones chemical structure

steroid hormones chemical structure

Diabetes results from inadequate levels of insulin. Type I diabetes is characterized by inadequate levels of insulin secretion, often due to a genetic cause. Type II usually develops in adults from both genetic and environmental causes. Loss of response of targets to insulin rather than lack of insulin causes this type of diabetes. Diabetes causes impairment in the functioning of the eyes, circulatory system, nervous system, and failure of the kidneys. Diabetes is the second leading cause of blindness in the US. Treatments involve daily injections of insulin, monitoring of blood glucose levels and a controlled diet.

Media:

steroid hormones chemical structuresteroid hormones chemical structuresteroid hormones chemical structuresteroid hormones chemical structuresteroid hormones chemical structure

http://buy-steroids.org