Hormones Flashcards
(42 cards)
Five major types of Hormones
(1) AMINO ACID DERIVATIVES
* dopamine, catecholamine, and thyroid hormone:
(2) SMALL NEUROPEPTIDES
* GnRH, TRH, somatostatin, and vasopressin:
(3) LARGE PROTEINS
* insulin, LH, and PTH:
(4) STEROID HORMONES
* cortisol and estrogen
(5) VITAMIN DERIVATIVES
* retinoids (vitamin A) and vitamin D
The glycoprotein hormone family illustrates many features of related hormones.
- thyroid-stimulating hormone (TSH}
- follicle-stimulating hormone (FSH)
- LH
- human chorionic gonadotropin (hCG)
The glycoprotein hormones are ___ that share the a subunit in common: the B subunits are distinct and confer specific biologic actions.
heterodimers
TSH interacts minimally with
LH or FSH receptors
Very high levels of hCG during pregnancy
stimulate the ___ receptor and increase thyroid hormone levels, resulting in a compensatory decrease in TSH.
TSH
Nuclear Receptor
(glucocorticoid receptor,
mineralocorticoid receptor, androgen receptor, estrogen receptor, progesterone receptor) that bind steroids
type 1 receptors
Nuclear Receptor
(thyroid hormone receptor,
vitamin D receptor, retinoic acid receptor, peroxisome proliferator activated receptor) that bind thyroid hormone, vitarnin D, retinoic
acid, or lipid derivatives.
type 2 receptors
Exceptions of Nuclear Receptor:
1.Glucocorticoid and mineralocorticoid receptors
2.Relaxed nuclear receptor specificity involves the estrogen receptor, which can bind an array of compounds, some of which have little apparent structural similarity to the high-affinity ligand
estradiol.
Classic Pathway of Gene Expression
transcription — MRNA — protein — posttranslational protein processing —
intracellular sorting, followed by membrane integration or secretion
Modifications of the precursor, cholesterol
Steroid Hormones
- diffuse into the circulation as they are synthesized.
- Thus, their secretory rates are closely aligned with rates of synthesis.
Steroid hormones
Circulating hormone half-life:
- T4:
- T3:
- Most protein hormones (e.g., ACTH, GH, PRL, PTH, LH) have
- T4:7 days
- T3:1 day
- Most protein hormones (e.g., ACTH, GH, PRL, PTH, LH) have relatively short half-lives (<20 min)
change the free hormone concentration, which in turn induces compensatory
adaptations through feedback loops.
Short-term perturbations in binding proteins
are an exception to this
self-correcting mechanism (insulin resistance / androgen excess)
SHBG changes in women
can reduce total thyroid hormone levels greatly but the free concentrations of T4 and 73 remain normal.
TBG deficiency
can also influence binding protein levels (e.g., estrogen increases TBG) or cause displacement of hormones from binding proteins (e.q., salsalate displaces T4 from TBG).
Liver disease and certain medications
inactivates glucocorticoids in renal tubular cells, preventing actions through the mineralocorticoid receptor
11B-hydroxysteroid dehydrogenase type 2
- are located almost exclusively in the adrenal cortex, and
- are found predominantly in the gonads
- are widely distributed, reflecting the need for metabolic responses in all tissues.
- ACTH receptors
- FSH receptors
- insulin and TRs
Membrane receptors for hormones can be divided into several major groups:
—seven transmembrane (GPCRs)
— Tyrosine kinase receptors,
— cytokine receptors
— serine kinase receptors
- of GPCRs vary widely in size and are the major binding site for large hormones.
- are composed of hydrophobic a-helical domains that traverse the lipid bilayer.
- is a docking site for G proteins.
- extracellular domains
- transmembrane- spanning regions
- intracellular domain
- G proteins form a ___ that is composed of various a and By subunits.
- Under these conditions, the Ga subunit is activated and mediates signal transduction through various enzymes, such as
- heterotrimeric complex
- adenylate cyclase and phospholipase C
- transduce signals for insulin and a variety of growth factors
- play a prominent role in cell growth and differentiation as well as in intermediary metabolism.
-Tyrosine kinase receptors
- GH and PRL receptors belong to this family.
- Analogous to the tyrosine kinase receptors, ligand binding induces receptor interaction w/ intracellular kinases- the Janus kinases (JAKs), w/c phosphorylate members of the signal transduction & activators of transcription (STAT) family- as well as with other signaling pathways (Ras, PI3-K, MAPK).
Cytokine receptor
- mediate the actions of activins, transforming
growth factor B, mullerian-inhibiting substance, and bone morphogenic proteins
-This family of receptors (consisting of type | and II subunits) signals through proteins termed smads- transducing the receptor signal and acting as transcription factors.
- act primarily in a local {paracrine or autocrine) manner.
Serine kinase receptors
