Chem: Section Section 11.1&2: Endocrine Function and Assoc. disorders

inhibition or suppression of the normal response of an organ or system

down-regulation

exposure of receptors to high concentration of hormone may decrease the number of surface receptors

desensitization

some hormones may have varying affinity levels- strong affinity for their own receptors and a weaker affinity for receptors of another hormone

specificity spill-over

What is the other name for growth hormone?

stomatotropin

a chemical substance released in the bloodstream, effects are seen at a site distant from the release

endocrine hormone

hormone released from endocrine cell into interstitial space, acts on neighboring cells

paracrine hormone

hormone synthesized in endocrine cells, bind to receptor within the cell of origin

autocrine hormone

hormone synthesized in endocrine cells, act on adjacent cells by direct cell-to-cell contact

juxtacrine hormone

hormone synthesized in endocrine cells, target is the gut, help with digestion

exocrine hormone

hormone synthesized in cells in the nervous system, act on sites distant from release

neuroendocrine hormone

What is the chemical structure of the following hormones? What is their solubility?

steroid

polypeptide

amine

steroid: lipid based (derived from cholesterol), water-insoluble

polypeptide: protein based, water-soluble

amine: derived from amino acid tyrosine, share properties in both

Where is the receptor for steroid hormones located?

inside the cell because the lipids can readily diffuse through the phospholipid membrane and enter the nucleus

Where is the receptor for polypeptide hormones located?

on the surface of the cell because they cannot diffuse through the cell like lipids can

What occurs when polypeptide hormones bind to the receptor outside the cell? What is the primary and secondary messenger?

adenylate cyclase is activated and produced cyclic AMP (cAMP), which then activates the protein/enzyme inside of the cell

primary messenger: hormone

secondary messenger: cAMP

Which hormone has a long half life? Which has a short half life?

steroid hormones have a long half-life, therefore take longer for action to occur (enzyme needs to be made)

polypeptide hormones have a short half-life, therefore have a quick action (enzyme already present in cell, just needs to be activated)

What amino acid are amine hormones derived from?

tyrosine

Amine hormones share properties from both steroid and polypeptide hormones. What are the protein-like amine hormones? What are the steroid-like amine hormones?

protein-like: epinephrine, norepinephrine, dopamine

steroid-like: T4 (thyroxine), T3 (triiodothyronine)

hormone receptor consisted of guanine nucleotide-binding protein; adenylate cyclase catalyzes the formation of cAMP which activates the enzyme already in the cell; require a primary and secondary messenger

nuclear receptors (G protein family)

hormone receptor that contains tyrosine kinase activity so bind to hormones that have a tyrosine base; phosphorylation reaction occurs (requires ATP)

membrane receptors (protein kinase)

the function of hormone A results in an increase in hormone B; not as common as negative feedback feedback mechanisms and rarely operate in isolation

positive feedback mechanism

concentration of hormone B causes a decrease in hormone A

negative feedback mechanism

What are the primary, secondary, and tertiary hormone regulation mechanisms?

tertiary: hypothalamus

secondary: anterior pituitary

primary: target endocrine gland

What general factors can affect hormone release and measurement?

*biorhythms*: circadian/diurnal, may have to take multiple measurements throughout the day

*autonomy*: hormones acting from something other than what normally controls like (e.g. tumor)

*protein binding*: not enough protein present to be used as a carrier molecule

*heterogeneity*: different form of a hormone cannot be measured

*assay limitations*: not sensitive enough, cross-react with other hormones

What two types of hormones does the hypothalamus secrete?

releasing hormones (turn on) and inhibiting hormones (turn off)

How are hormones measured in the lab?

immunoassay

Which hormones are released from the posterior pituitary? (2)

ADH, oxytocin

Which hormones are released from the anterior pituitary? (5)

TSH, ACTH, reproductive hormones, growth hormone (GH), prolactin (PRL)

Which hormones are secreted by the adrenal medulla? (3)

catecholamines (epinephrine, norepinephrine, dopamine)

Which hormones are secreted by the adrenal cortex? (4)

aldosterone (mineralcorticosteroid), cortisol (glucocorticoid), progesterone and estrogen

What is the master gland?

anterior pituitary

most abundant hormone produced by the anterior pituitary

growth hormone

GH mediates its anabolic and metabolic reactions through the intermediary ________________, causing growth

insulin-like growth factor (IGF-1)

increase in GH that results in elongation and enlargement of bones of the extremities, certain head bones such as frontal bones and jaw; enlargement of nose and lips; thickening of soft tissue of the face

acromegaly

elevated levels of GH occurring before long-bone growth is complete

pituitary gigantism

How are acromegaly and pituitary gigantism diagnosed?

failure of GH suppression within 1-2 hours after a glucose load (hyperglycemia should suppress GH normally)

Decreased levels of growth hormone result in short stature in children. How is this diagnosed?

Diagnose with insulin-based hypoglycemia test (hypoglycemia triggers the release of GH normally)

hormone responsible for initiation and maintenance of milk production; produced by lactrotrophs in anterior pituitary

prolactin

What is related to an increase in prolactin? (5)

Amenorrhea, galactorrhea, infertility, pregnancy, medications

What causes a decrease in prolactin?

should be low normally. only increased when pregnant or breast-feeding

spontaneous milk production from breasts

galactorrhea

sensitive indicator of pituitary dysfunction and the hormone most frequently produced in excess by pituitary tumors; first hormone to become deficient from infiltrative disease or tumor compression of the pituitary

prolactin

hormone responsible for increased production and release of corticosteroids

ACTH

What is the other name for ADH?

vasopressin, or arginine vasopressin

regulator of fluid and electrolyte balance, retains water (and therefore sodium)

ADH (vasopressin)

increase in ADH, caused by malignancy, CNS tumors, or drug therapies

syndrome of inappropriate antidiuretic hormone secretion (SIADH)

How is SIADH tested?

urine osmolality > plasma osmolality, decreased plasma sodium and increased urine sodium

(remember ADH retains water which will dilute blood and concentrate urine)

condition characterized by copious production of urine (polyuria) and accompanied by intense thirst (polydipsia) because of ADH deficiency

diabetes insipidus

What is the difference between central and nephrogenic diabetes insipidus? How can lab testing differentiate the two?

central DI: posterior pituitary not producing enough ADH

nephrogenic DI: kidney not reabsorbing ADH

overnight water-deprivation test:

central DI: kidneys will conserve water

nephrogenic DI: symptoms will continue

contributes to the contraction of uterine smooth muscle and stimulates epithelial cells surrounding the mammary glands, resulting in milk ejection

oxytocin

What is the precursor of cortisol?

cholesterol

What are the functions of cortisol?

raises carbohydrate and fat metabolism; raise blood glucose levels by suppressing secretion of insulin, inhibit cellular uptake of glucose, promote hepatic glucose synthesis; stimulates the production of fatty acids via cellular lipase activation. Also has anti-inflammatory activities, which include suppression of cytokines, release of WBCs from bone marrow but inhibition of their transport through capillary walls, decrease of eos and T-lymphs

What are the common S/S of an increase in cortisol? What is hypercortisolism commonly termed?

Cushing's disease

S/S: moon face, bruising, poor wound healing, muscle weakness, depression, trunkal obesity, buffalo hump

What is a decrease in cortisol termed?

Addison's disease

What is the difference between 1 and 2 degree hypercortisolism?

1 degree hypercortisolism: Cushing's syndrome, ACTH independent (adrenal gland produces too much): adrenal tumors, overuse of glucocorticoids, chronic alcoholism, stress, obesity

2 degree hypercortisolism: Cushing's disease, ACTH dependent (anterior pituitary releasing too much ACTH): benign hormone-secreting pituitary adenoma

What is the difference between 1 and 2 degree hypocortisolism?

1 degree hypocortisolism: increased ACTH and decreased cortisol (adrenal gland not producing enough): usually due to autoimmune destruction, can also be neoplasm or metabolic defects or meds

2 degree hypocortisolism: decreased ACTH and decreased cortisol (anterior pituitary not producing enough): caused by surgical removal of pituitary and head trauma