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endicrinology
study of endocrine glands and the physiological effects of their hormone secretions
hormone secretions influenced by hypothalamus and pituitary gland (hypophysis) in the brain in the central nervous system
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Hormones:
Chemical substances formed in one organ part of the body and carried in the blood to another organ or body part
chemical messengers
signal certain tissues to grow or change their cellular activity
can alter or change the structure or functional activity of one organ or more
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what kind of hormones are there?
- proteins
- smaller polypeptides
- peptides
- amines from amino acids
- some come from fatty acids
- Steroid hormones come from cholesterol
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what type of steroid hormones is there?
- Androgens:promote the development and function of the male reproductive structures
- Estrogens: stimulate the maturation and the function of the female reproductive structures
- Progestogens:Cause the uterus to be secretory and supports pregnancy
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paracrines are :
chemical messengers produced by the endocrine cells and diffuse to act LOCALLY on ADJACENT cells
Unlike hormones, PARACRINES ARE NOT CARRIED IN THE BLOOD STREAM
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Protein and peptide hormones bind to:
- receptors embedded in the cell membrane of responsive cells
- (GnRH): Gonadotropin releasin hormones
- (FSH): follicle stimulating hormones
- (LH): luteinizing hormone
- (PRL): prolactin
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Protein and Peptine Hormone receptors have 3 major domains, what are they?
- Extracellular
- Transmembrane
- Intracellular
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extracellular domain:
hormonal signal is received when ligand attaches to ligand binding site in extracellular membrane that sticks out beyond the cell
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Transmembrane Domain:
anchors receptor WITHIN plasma membrane
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Intracellular domain:
extension of receptor protein within the cell cytoplasm
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Signal transduction:
TRANSLATION of a hormone message to the interior of the cell with FIRST MESSENGER that causes a CONFORMATIONAL CHANGE that triggers a BIOCHEMICAL change in the cell cytoplasm that RELEASES THE SECOND MESSENGER
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Steroid Hormones are: estrogen, testostorone, and progesterone.
They are:
- Lipid Soluble
- Pass through phospholipid bilayer of the plasma membrane
- Steroid receptors are located within the cytoplasm or nucleus of target cells
- When it binds to its receptor, it undergoes a conformational change that exposes DNA binding domain
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Transcription means:
Transfer of the genetic code information from one kind of nucleic acid to another.
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Translation Definition:
- A Change or conversion to another form
- Complex process by which Messenger RNA, transfer RNA, and ribosomes effect the production of amino acids, the specificity of synthesis being controlled byh the base sequences of the messenger RNA
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Are Steroid or Protein and Peptide Hormones faster?
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Biological activity of Steroid Hormones in a Tissue Depend on:
- Local concentration of hormone
- Number of receptors for hormone that are present
- Cells can gain or lose receptors
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Estradiol, Estriol and Estrone
are 3 endogenous estrogens. They Have different affinities though. Which has the strongest affinity to receptors? Weakest?
- Strongest: Estradiol
- Weaskest: Estrone
- Estriol has 10% affinity
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Sex Steroid BINDING GLOBULINS:
- Gonadal Steroid Hormones secreted into the blood circulation and quickly attached to SEX STEROID BINDING GLOBULINS which are carrier proteins in the blood.
- Availability of Steroid Hormones to target cells is regulated by the concentration of carrier proteins (SEX STEROID BINDING GLOBULINS)
- Concentration of carrier proteins changes with pregnancy and obesity
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There are exogenous molecules that influecne hormone receptors. Like Phytoestrogens (from soy) and Xenoestrogens (human made chemicals). There is 3 types:
- Synthetic Analogs: Molecules synthesized by chemists that are similar to estrogen
- Agonists stimulate estrogen receptors
- Antagonists block estrogen receptors
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Estradiol
Tamoxifen
Raloxifene
- activates Bone Breast and Uterine estrogen receptors.
- activates bone and uterine receptors
- Activates bone receptors
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