Exam 4 Flashcards
Endocrinology
Study of intra and extracellular communication by hormones
Hormone
Chemical substance produced and secreted into the blood by an endocrinological organ or tissue
Endocrine hormone
Synthesized in 1 location and released into blood circulation, binds to specific receptor in cells at a distant site to elicit response
Paracrine hormone
Synthesized in endocrine cells and released into interstitial space, binds to specific receptor of nearby cell and affects it function
Autocrine hormone
Synthesized in endocrine cells and sometimes released into interstitial space, binds to specific receptor on the cell of origin autoregulating its function
Exocrine hormone
Synthesized in endocrine cells and released into lumen of GI, binds to cells lining the GI at varying distances from the endocrine cells affecting their functions
Function of hormones
Maintain homeostasis for efficient function, influence growth and development, part of overall control of bodily function, linked to CNS through hypothalamus and pituitary to regulate and respond to target organs
Mechanism of action of hormones
Binding of a hormone to its receptor on the surface of the cell membrane through cAMP or Phospholipase C pathway
Bioassay
Based on observations of physiological responses that are specific for the hormone being measured
Immunoassay
ELISA. RIA, EMIT, fluorescence polarization and chemiluminescent immunoassay
Radioreceptor assay
An in vitro assay which allows interaction of hormone with its biological receptor
Hypothalamic-pituitary axis location
The portion of the brain located in the walls and floor of the third ventricle, which is connected to the posterior pituitary by the pituitary stalk
Hypothalamic-pituitary axis purpose
Control over pituitary function by direct neurostimulation and neurosecretion events of the hypothalamus, direct relationship with posterior pituitary, indirect relationship with anterior pituitary through the portal system
Pituitary location
Below the hypothalamus anatomically
Pituitary function
Releases hormone such as ADH, oxytocin, ACTH, GH, prolactin, LH, FSH and TSH
General features of over-secretion of pituitary hormones
Overproduction of only 1 hormone, deficient in more than 1 and eventually all the anterior pituitary hormones, sequentially loss of hormones, GH - FSH - LH - TSH - ACTH and prolactin, delayed diagnosis due to slow development of symptoms
Growth hormone physical actions
Promotes growth in soft tissues, cartilage and bone, causes positive nitrogen and phosphorous balance, stimulates hepatic glycogenolysis and antagonizes the effect of insulin on glucose uptake by peripheral cells, promotes linear growth through other hormone factors
Insulin-like growth factors
Polypeptides structurally related to insulin, exhibit metabolic and growth promoting effects similar to insulin
IGF I
One of the major regulators of cell growth and differentiation, synthesis mainly in liver, dependent on GH
Regulation of GH
Stimulated by GHRH, inhibited by somatostatin
Over-secretion of GH
By adenomas of pituitary, impairment of glucose tolerance
Pituitary giant
If overproduction occurs before long-bone growth is complete
Acromegaly
If overproduction occurs after long-bone growth is complete, prior to closure of epiphyseal plates
GH deficiency as an isolated disorder
Pituitary dwarfism in children, no clinical symptoms in adult