Hormones 2 & 3 Flashcards
What is the master control center of the endocrine system?
What is its target organ?
hypothalamus
Target organ: Pituitary
Hypothalmic hormones stimulate what aspect of the pituitary?
anterior pituitary
How do hypothalmic hormones stimulat the release of pituitary horomnes?
stimulate exocytosis of pre-existing vesicles containing the various anterior pituitary hormones
What are the 7 hypothalamus hormones?
- Thyrotropin-Releasing hormone
- Prolactin-releasing hormone
- Prolactin release-inhibiting hormone
- Corticotropin-releasing hormone
- Gonadotropin-releasing horomone
- Growth hormone-releasing hormone
- Somatostatin
Thyrotropin-releasing horomone (TRH) has what effect on the pituitary?
Stimulates release of Thyroid Stimulating Horomone (TSH)
Prolactin-releasing factor (PRF) has what effect on the pituitary?
stimulates the release of prolactin (PRL)
Prolactin release-inhibiting horomone (PIH) has what effect on the pituitary?
Inhibits the release of prolactin (PRL)
Corticotropin-releasing horomone (CRH) has what effect on the pituitary?
Stimulates release of Adrenocorticotropic hormone (ACTH)
Gonadotropin-releasing horomone (GnRH) has what effect on the pituitary?
stimulates the release of Lutenizing hormone (LH) and Folicle-stimulating hormone (FSH)
Growth hormone-releasing horomone (GHRH) has what effect on the pituitary?
Stimulates the release of Growth Hormone (GH)
Somatostatin (SS) hormone has what effect on the pituitary?
Inhibits the release of Growh hormone (GH)
What are the characteristic features of the releasing horomones?
- cyclic N-terminal
- C-terminal is an amide instead of a free carboxylic acid group
- generally stimulate Ca2+, IP3, PKC-linked pathway in anterior pituitary
What are the divisions of the pituitary?
anterior pituitary
posterior pituitary
incomplete intermediate lobe
What are the 6 hormones released by the anterior pituitary & what are their respective target organs?
- Thyroid Stimulating Hormone (TSH)
- thyroid
- Prolactin (PRL)
- mammary gland
- Adrenocorticotrophic Hormone (ACTH)
- adrenal cortex
- Lutenizing Hormone (LH)
- sex organs
- Folicule Stimulating Hormone (FSH)
- sex organs
- Growth Hormone (GH)
- bone, muscle, adipose tissue
What are the 2 protein hormones released by the anterior pituitary?
GH and Prolactin
GH has what type of receptor?
Single membrane pass receptor
Generates Jak/STAT cascade
What are the 3 glycoprotein hormones released by the pituitary?
Describe their subunit composition.
TSH, FSH, and LH
hetero dimer (alpha & beta subunits)
alpha subunits are all the same, but the beta is different & provides the biological activity
the beta subunit is NOT active without the alpha subunit
TSH, FSH, and LH utilize what type of receptor system?
Gs
adenylyl cyclase stimulated cAMP pathway
What is POMC & where is it expressed?
Pro-opiomelanocortin
285 aa precursor that can undergo differential processing to yield at least 8 peptides
expressed in both the anterior and intermediate lobes of the pituitary
What hormones are derived from POMC?
-
ACTH
- main physiologically active product of CRH
-
MSH (melanocyte stimulating hormone)
- stimulates melanin synthesis in the skin
-
Lipotropin
- promotes release
-
Endorphins
- decreases pain perception & euphoria
In what ways is POMC processed?
glycosylations
acetylations
extensive proteolytic cleavage @ basic protein sequences (tissue specific)
How are different products produced from POMC if they are all produced in the pituitary?
DIfferent cell types within the pituitary express different proteolytic activities which produce the different products
What horomones are produced in the hypothalamus & stored in the posterior pituitary?
They are associated wtih what carrier proteins?
Oxytocin & Vasopressin (ADH)
carrier proteins: neurophysins
How do oxytocin & vasopressin reach their target organs?
they are secreted directly into the systemic circulation
What type of hormone is ADH?
What is its main function?
cyclic nonapeptide
main regulator of body fluid osmolarity
What type of hormone is oxytocin?
What is its major function in the body?
cyclic nonapeptide
Stimulates lactation, uterine contraction during delivery
A deficiency in ADH causes what disease?
Diabetes insipidus
A dietary deficiency of iodine woudl result in excess secretion of what hormone?
Thyroid Stimulating Hormone
What are the iodinated dityrosine derivatives?
thyroxine and triiodothyronine
The thyroid hormones are released in response to what messenger?
They stimulate what action?
Respond to TSH adn stimulate oxidations in many cells
How are the tyhroid hormones synthesized & excreted?
they are synthesized from tyrosyl residues in thyroglobulin
thyroglobulin is exocytosed
How is iodine concentrated in the cells of the thyroid?
Na+/K+-ATPase-driven pump pumps Na+ outside of the cell
When Na+ reenters the cell, it brings iodide with it via the sodium iodide symporter (NIS)
So, as Na+ continually gets pumped out, iodide gets concentrated in the thyroid cells
Iodide is transported to what location in the thyroid?
Iodide is trasnported to the follicle lumen
What enzyme oxidizes iodide to I+?
Where is this enzyme located?
thyroperoxidase
found only in thyroid tissue
What enzyme catalyzes the I+ tyrosine residues?
This leads to what two products?
thyroperoxidase
thyroglobulin containing monoiodotyrosyl (MIT) and diiodotyrosyl (DIT) residues