Patho II Endocrine Exam 3

type of hormone synthesized from cholesterol or arachidonic acid

steroid/lipid based hormones

type of hormone synthesized as a prohormone, needing further processing to become active

peptide hormones

what type of hormone is synthesized from tyrosine or tryptophan

amino acid based hormones

what type of hormone is stored in vesicles (regulatory secretion)

peptide hormones

what type of hormone is released immediately (constitutive secretion)

steroid/lipid based hormones

what type of hormone requires carrier proteins to travel through blood

steroid/lipid based hormones and thyroid hormones

what type of hormone is mostly water soluble and can travel freely through the blood

peptide hormones

example of a polar amino acid derived hormone

epinephrine (adrenaline)

where do thyroid hormones bind to receptors

intracellularly

insulin, glucagon, prolactin, and ACTH are all examples of

peptide hormones

cortisol, aldosterone, estrogen, progesterone, and testosterone are all examples of

steroid/lipid based hormones

epinephrine (adrenaline), thyroxin, and triiodothyronine are all examples of

amino acid derived hormones

hormones that bind to plasma membrane receptors and use second messengers to transmit signal

peptide hormones, epinephrine (adrenaline), eicosanoid (from arachidonic acid)

hormones that bind to nuclear receptors and control transcriptional translation

steroid/lipid based hormones, Vitamin D, thyroid hormones, triiodothyronine, retinoid

MOA of nitric oxide signalling

binds to cytosolic receptor guanylyl cyclase and uses secondary messenger cGMP

effects of free radical nitric oxide

vasodilator, increased blood flow and decreased BP

what happens when blood osmolarity is too high

hypothalamus releases ADH (vasopressin) causing kidneys to reabsorb more water

what happens when blood Ca2+ decreases

parathyroid glands secrete PTH (parathyroid hormone) causing increased Ca2+ reabsorption in the kidneys

CaSR activity in the normal parathyroid gland

Ca2+ binds to CaSR receptor, inducing Gα q/11-mediated activation of phospholipase C. this causes inc. IP3 and intracellular Ca2+ mobilization suppressing PTH synthesis. dec. Ca2+ levels induce PTH synthesis.

catecholamines

dopamine, epinephrine, norepinephrine

hormones are synthesized and released in response to

humoral, neural, and hormonal stimuli

hormones are removed from the blood by

degrading enzymes, kidneys, liver

permissiveness

one hormone allows or enhances the effects of another, the presence of the permissive hormone is necessary for the expression of the other

synergism

the action of two hormones results in activity greater than the sum of the activity of each alone

antagonism

one or more hormones opposes the action of another

function of ACTH (adrenocorticotropic hormone)

regulate levels of cortisol release form adrenal glands

desensitization

biological response to a drug diminishes when given continuously/repeatedly

homologous desensitization

only agonist-activated receptors are desensitized

heterologous desensitization

both agonist-activated and non-activated receptors sharing the same signalling pathways are inactivated

mechanisms of desensitization

• downregulation of receptors

• receptor modification

• receptor endocytosis

• inhibition of signal transduction

function of hypothalamus

indirect control of homeostasis through secretion of tropic (regulatory) hormones - releasing hormones or inhibiting hormones

how are regulatory hormones transported from hypothalamus to anterior pituitary

hypophyseal portal system, secreted into the primary capillary plexus

where is CRH (corticotropin-releasing hormone) secreted

hypothalamus

where is TRH (thyrotropin-releasing hormone) secreted

hypothalamus

where is GH-RH (growth hormone-releasing hormone) secreted

hypothalamus

where is GH-IH (growth hormone-inhibiting hormone) aka somatostatin secreted

hypothalamus

where is PRF (prolactin-releasing factor) secreted

hypothalamus

where is dopamine (PRF: prolactin-releasing hormone) secreted

hypothalamus

where is GnRH (gonadotropin-releasing hormone) secreted

hypothalamus

where is ACTH (adrenocorticotropic hormone) secreted

anterior pituitary

glucocorticoids are secreted from

adrenal glands in response to ACTH

where is TSH (thyroid stimulating hormone) secreted

anterior pituitary

function of TSH

regulating the amount of thyroid hormones secreted from thyroid

where is GH (growth hormone) secreted

anterior pituitary

where is PRL (prolactin) secreted

anterior pituitary

where is FSH (follicle stimulating hormone) secreted

anterior pituitary

where is MSH (melanocyte stimulating hormone) secreted

anterior pituitary

where is ADH (antidiuretic hormone) aka vasopressin secreted

posterior pituitary

where is oxytocin secreted

posterior pituitary

where is LH (luteinizing hormone) secreted

anterior pituitary

how do hormones secreted in anterior pituitary reach systemic circulation

secretes hormones into the secondary capillary plexus

how are hormones released from the posterior pituitary into the bloodstream

hormones (oxytocin, vasopressin) synthesized in hypothalamus and stored in axon terminals in the posterior pituitary, released when hypothalamic neurons fire and action potentials arrive at axon terminals

another name for anterior pituitary

adenohypophysis

another name for posterior pituitary

neurohypophysis

nonapeptide hormones

vasopressin and oxytocin

function of oxytocin

• stimulates uterine contractions

• triggers mammary glands to eject milk (“letdown” reflex) - positive feedback loop from babies suckling

• “love” hormone - acts as neurotransmitter in the brain

• used to induce labor - pitocin

• uterotonic drug - stimulates muscular tone in uterus to prevent postpartum hemorrhage

vasopressin is released from the posterior pituitary in response to

• increased plasma osmolarity (hypernatremia)

• reduction in blood pressure

• decreased volume of circulating blood (hypovolemia)

where does vasopressin bind

• V1a receptors on vascular smooth muscle cells, induces vasoconstriction

• V2 receptors in the principal cells of the collecting duct in kidneys

signal cascade when vasopressin binds ro V2R in kidney principal cells

triggers cAMP pathway, phosphorylation of AQP2 (aquaporin) and movement to apical membrane to facilitate water reabsorption

ADH (vasopressin) deficiency causes

diabetes insipidus (DI)

central diabetes insipidus

due to impaired secretion of vasopressin (ADP/AVP), possibly from traumatic brain injury, surgery, tremors

nephrogenic diabetes insipidus

due to failure of the kidney to respond to vasopressin (ADP/AVP), usually inherited

syndrome of inappropriate ADH secretion (SIADH)

vasopressin (ADH) hypersecretion

why don’t patients with SIADH exhibit edema and remain euvolemic

regardless of increased water retention, kidneys increase salt excretion in the urine, osmotically attracting water to be excreted as well

dilutional hyponatremia

decreased sodium levels in the blood in patients with SIADH, also due to some medications and excess water intake

T or F: all hormones secreted from the anterior pituitary are proteins

true

gonadotropins

FSH and LH

tropic hormones

regulate the secretory action of other endocrine glands

signalling pathways of hormones secreted from anterior pituitary

all hormones except GH activate cAMP second messenger pathways

tropic hormones secreted from anterior pituitary

TSH, ACTH, FSH, LH

direct actions of GH

metabolic, anti-insulin: increased fat breakdown/release and increased BG

indirect actions of GH

growth promoting: stimulates liver to produce IGF-1 which causes increased skeletal growth, cartilage formation, protein synthesis, cell proliferation

thyrotropin (thyroid-stimulating hormone) secretion is stimulated by

thyrotropin-releasing hormone (TRH)

thyrotropin (thyroid-stimulating hormone) secretion is inhibited by

rising blood levels of thyroid hormones

function of FSH

stimulates gamete production

function of LH

promotes production of gonadal hormones

what inhibits the release of prolactin

dopamine (PIH)

disorders from hyperactivity of the anterior pituitary

gigantism, acromegaly, Cushing’s disease

disorders from hypoactivity of the anterior pituitary

dwarfism, acromicria, Simmond’s disease

disorders from hyperactivity of posterior pituitary

SIADH

disorders from hypoactivity of the posterior pituitary

diabetes insipidus

disorder from the hypoactivity of the whole pituitary

dystrophia adiposogenitalis

what do pinealocytes in the pineal gland secrete

melatonin

precursor to ACTH

pro-opiomelanocortin (POMC) polypeptide, cleaved differently to serve different functions

where is the segment of POMC that becomes ACTH processed

the intermediate lobe of the pituitary

where is the segment of POMC that becomes MSH (melanocyte-stimulating hormone) processed

anterior and intermediate lobes of the pituitary

where is the segment of POMC that becomes β-LPH processed

fast in the intermediate lobe of the pituitary, slow in the anterior lobe

function of adrenal cortex

secretes steroid hormones (aldosterone and cortisol) and sex hormones

function of adrenal medulla

secretes epinephrine (75-80%) and norepinephrine (20-25%)

layers of the adrenal cortex superficial to deep

• Capsule

• zona Glomerulosa

• zona Fasciculata

• zona Reticularis

• adrenal Medulla

what layer of the adrenal cortex secretes glucocorticoids like cortisol

zona fasciculata

what layer of the adrenal cortex secretes mineralocorticoids like aldosterone

zona glomerulosa

what layer of the adrenal cortex secretes sex hormones (or glucocorticoids)

zona reticularis

function of mineralcorticoids

regulates electrolyte excretion in the kidney (primarily Na+ and K+), affecting blood pressure and blood volume

most potent mineralocorticoid

aldosterone

function of aldosterone

stimulates Na+ reabsorption, elimination of K+, and water retention in the kidneys

what induces the production of steroid hormones in the adrenal cortex

ACTH from the anterior pituitary

T or F: the zona glomerulosa in the adrenal cortex is the only area with the CYP11B2 enzyme and thus the only area that can synthesize aldosterone

true

how does aldosterone regulate Na+ and H2O reabsorption

activation of mineralocorticoid receptor causes increased gene transcription of Na+ channels (ENaC) and Na+/K+ ATPase on distal tubules and collecting ducts of kidneys; drives Na+ reabsorption and thus water reabsorption

how does aldosterone regulate K+ excretion

stimulating Na+/K+ ATPase activity and upregulating the renal outer medullary K channel (ROMK)