Endocrine System: Pathophysio

homeostasis

the body's attempt to maintain a "balance" for optimal cell, organ and system functioning

2 systems maintaining homeostasis

nervous and endocrine

secreted by the endocrine system

hormones

primary endocrine organs

-Hypothalamus
-Pituitary gland
-Pineal gland
-Thyroid gland
-Adrenal gland
-Pancreas
-Gonads (ovaries/testicles)

secondary endocrine organs

-Heart
-Brain
-Stomach
-Liver
-Kidney
-Intestines
-Adipose tissue

hormones

regulatory molecules that are secreted by endocrine glands

target organs

organs that respond to hormones

goal of endocrine hormones

endocrine hormones travel through blood to target organs, and their action causes a "reaction" within the target organ

all organs in the body receive hormones, but only some respond because they have the corresponding receptors for that hormone. (T/F)

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2 types of hormones

-non-polar (lipid soluble)
-polar (water soluble)

non-polar hormones

-insoluble in water (lipid soluble); does cannot dissolve in blood plasma

-soluble in other non-polar molecules (i.e. lipids)

-bound to carrier proteins in blood

-can be taken orally and absorbed through intestines into blood

types of non-polar hormones

steroids and thyroid

steroids

-secreted by adrenal cortex and gonads
-derived from cholesterol

thyroid

-primarily thyroxine
-derived from tyrosine and have iodine

how non-polar hormones work

-can cross plasma cell membrane of target cell

-receptor proteins are located inside the cell

-nuclear receptors: hormone binding triggers receptor to move to nucleus which binds to DNA, activating genes to produce proteins

polar hormones

-soluble in water = can dissolve in blood plasma
-able to be carried into their target organ
-cannot be taken orally or will be digested

types of polar hormones

catecholamines, polypeptides, proteins, and glycoproteins

catecholamines

epinephrine, norepinephrine, L-dopa

polypeptides

insulin

proteins

growth hormone

glycoproteins

luteinizing hormone

how polar hormones work

-cannot cross plasma cell mrbane of target cell
-plasma cell membrane has receptor proteins in it that bind hormones in extracellular fluid
-binding activates the secondary messenger systems--> caries out the hormone's effect

what is the medical implication of the secondary messenger system (with polar hormones)?

the secondary messenger is too polar to cross the cell membrane; therefore, hormone treatment is necessary (cannot simply activate the messenger)

hypothalamus

control center of the brain

hypothalamus functions

-controls anterior pituitary by hormones and posterior pituitary gland via neural input
-provides blood flow to the pituitary = hypothalamus-hypophyseal portal system

hormones of the hypothalamus

-corticotropin-releasing hormone (CRH)
-thyrotropin-releasing hormone (TRH)
-gonadotropin-releasing hormone (GnRH)
-growth-hormone-releasing hormone (GHRH)
-somatostatin
-protein-inhibiting hormone (PIH)

corticotropin-releasing hormone (CRH)

stimulates anterior pituitary to secrete ACTH

thyrotopin-releasing hormone (TRH)

stimulates anterior pituitary to secrete thyroid stimulating hormone (TSH)

gonadotropin-releasing hormone (GnRH)

stimulates anterior pituitary to secrete gonadotropic hormone (FSH & LH)

growth-hormone-releasing hormone (GHRH)

stimulates anterior pituitary to secrete growth hormone (GH)

somatostatin

inhibits anterior pituitary gland from secreting growth hormone

protein-inhibiting hormone (PH)

inhibits anterior pituitary from secreting prolactin

pituitary gland location

-below hypothalamus
-attached to hypothalamus by infundibulum

pituitary gland is regulated by ____________

hypothalamus

pituitary glands

2 glands; anterior and posterior

anterior pituitary gland

-controlled by hormones secreted by the hypothalamus
-secretes its own hormones that regulate other endocrine glands

posterior pituitary gland

secretes hormones produced by neuron bodies in hypothalamus (which are transported into posterior pit. by axons)

organs affected by hormones of the posterior pituitary gland

-breast (mammary glands)
-uterus
-kidneys

organs affected by hormones of the anterior pituitary gland

-bones & soft tissues
-reproductive organs (gonads/ovary)
-thyroid gland
-adrenal gland

hormones of anterior pituitary

-produces and secretes "trophic" hormones
-if too high = causes excess growth of target organ
-if too low = causes target organs to shrink

types of hormones secreted by anterior pituitary

-growth hormone (GH)
-thyroid stimulating hormone (TSH)
-adrenocorticotropic hormone (ACTH)
-follicle stimulating hormone (FSH)
-luteinizing hormone (LH)
-prolactin

growth hormone (GH)

stimulates protein synthesis and tissue/organ growth

thyroid stimulating hormone (TSH)

stimulates thyroid to secrete its hormones (T3 & T4)

adrenocorticotropic hormone (ACTH)

stimulates adrenal cortex to secrete corticosteroids

follicle stimulating hormone (FSH)

stimulates growth of ovarian follicles and production of sperm

luteinizing hormone (LH)

stimulate ovulation and formation of corpus luteum in women; stimulates Leydig cells in men to produce testosterone

prolactin

stimulates milk production by mammary glands and inhibits ovulation

hormones of posterior pituitary

-produced, stored and secreted by hypothalamus
-antidieuretic hormone (ADH) and oxytocin

antidiuretic hormone (ADH)

aka vasopressin; acts on kidneys to promote water retention

oxytocin

stimulates contraction of uterus during labor and contraction of mammary ducts during lactation

how the hypothalamus controls the anterior pituitary gland

negative feedback loops to control homeostasis

pituitary pathologies

-inadequate GH
-over secretion of GH

inadequate GH pathologies

-Dwarfism: lack of growth in children

-Simmonds: premature aging in adults

over secretion of GH

-Gigantism: too much growth in children

-Acromegaly: thickening of bones and soft tissue growth in adults

pituitary cachexia (Simmonds disease) signs and symptoms

-progressive loss of skeletal muscles (without or with fat loss)
-low appetite
-unintentional weight loss/muscle wasting

pituitary cachexia (Simmonds disease) causes

-chronic inflammatory response
-cancer
-chronic illness (kidney disease, heart failure, COPD)

pituitary cachexia (Simmonds disease)

hypercatabolic syndrome affecting the pituitary gland

acromegaly

abnormal enlargement of the extremities (i.e. enlarged nose/lips/tongue, prominent forehead and chin/jaw)

adrenal gland basics

-located on top of kidneys
-two glands (one inside the other) --> adrenal cortex and adrenal medulla

adrenal cortex

-outer layers
-not innervated by axons
-secretes corticosteroids
-assist in regulating metabolism and electrolytes

adrenal medulla

-inner core
-innervated by sympathetic axons
-secretes epinephrine and norepinephrine
-assist in fight or flight

adrenal cortex hormones

glucocorticoids, mineralcorticoids, weak androgens

glucocorticoids

-increase blood glucose by breakdown of liver glycogen and conversion of non-carbohydrates to glucose)
-primarily cortisol (aka hydrocortisone)

mineralcorticoids

-regulate mineral and electrolyte concentrations in blood
-primarily aldosterone

weak androgens

-promote sex drive in women and puberty in men
-primarily androstenedione (converted to testosterone or esterone)

regulation of adrenal cortex

-negative feedback loop
-hypothalamus secretes CRH (corticotropin-releasing hormone)
-CRH triggers ACTH secrteted by anterior pituitary
-ACTH triggers adrenal cortex to release cortisol
-cortisol and ACTH provide negative feedback to slow or stop secretion of CRH by hypothalamus

cortisol (hydrocortisone)

suppresses inflammation and immune response

natural glucocorticoid

cortisol

man-made glucocorticoid

prednisolone & desamethasone

general adaptation syndrome (GAS)

-occurs in response to stress
-higher brain centers push increase of CRH secretion, thus ACTH when stressed
-increased cortisol means increased glucose for CNS and increased amino acids for tissue repair

medical implications of general adaptation syndrome (GAS)

-stress induced cortisol levels can be 6x as great as non-stressed levels
-can be detrimental as it suppresses immunity (increase risk of infection)

cortisol medication precuations

forms reduced natural cortisol secretion due to negative feedback loop -- drug must be tapered slowly

aldosterone

secreted by adrenal cortex

key functions of aldosterone

-retain sodium and water in blood (too little = dehydration)
-excrete potassium in urine (too much K+ in blood = heart fibrillation)

chemical regulators (chemical signals) leading to aldosterone secretion

-rise in K+ stimulates adrenal cortex to secrete aldosterone
-blood volume and pressure decrease triggers secretion of chemical, causes aldosterone to be secreted

adrenal pathologies

-Cushings
-Addisons

Cushing's disease

-oversecretion of ACTH

-sx: weakness, bone pain, back pain

-signs: moon face, hair growth, central obesity with abdominal/leg striae, easy bruising, thin extremities, personality changes, kyphosis

Addison's disease

-undersecretion of ATCH = electrolyte imbalance & dehydration

-sx: weak, hypotensive, weight loss, nausea, vomiting

-signs: "tanning" of pale skin, changes in distribution of body hair, weight loss

Emergent - addisonian crisis:

magnification of signs and symptoms in response to trauma, infection, and infarction which can lead to hypovolemic shock

PT concerns for Addison's disease

-no aquatic therapy
-monitor vitals
-watch for signs of infection

adrenal crisis (Addison's disease)

Profound fatigue, dehydration, vascular collapse (decrease BP), renal shut down, Na+ decrease and K+ increase

thyroid gland

-thyroid follicles trap iodine to make (thyroxine -T4, triiodothyronine-T3)
-non-polar: utilizes carrier protein to circulate blood
-thyroid stimulating hormone (TSH) from anterior pituitary stimulates follicles to secrete hormone

thyroid gland and homeostasis

hormone levels rise = negative feedback turns off anterior pituitary stimulation

functions of thyroxine

-required for correct growth and development in kids, especially the CNS
-stimulates cell respiration to "set" basic metabolic rate (BMR)

Goiter pathology

growth of thyroid gland due to stimulation from high TSH

2 major causes of goiter

hypothyroidism and hyperthyroidism

hypothyroidism

-insufficient iodine so thyroxine and T3 not, and TSH keeps elevating to send "signal" that blood levels are low and more should be made
-Hashimoto's disease (autoimmune)

hyperthyroidism

-antibodies stimulate thyroid to grow and overproduce thyroxine
-Graves disease

classic sign of Graves disease

bulging eyes

parathyroid glands

-4 on the back surface of thyroid glands
-secrete parathyroid hormone (PTH)
-regulates blood levels of Ca2+ and phosphate

how the parathyroid glands regulate blood levels of Ca2+ and phosphate levels

-absorption from food in intestine
-some deposited in bones
-some removed from bones

parathyroid function

-drop in blood Ca2+ triggers parathyroid to secrete PTH
-PTH stimulates osteoclasts to resorb bone and stimulates kidneys to retain Ca2+ (not lose it in urination)
-blood Ca2+ rises

pancreas gland

-pancreatic islets (islands of endocrine glands in pancreas)
-both hormones secreted regulate metabolism

pancreatic islets (Islets of Langerhans)

islands contain endocrine cells: alpha cells (secrete glucagon) and beta cells (secrete insulin)

basics of metabolism

-two processes acting antagonistaclly to one another
-anabolism
-catabolism
-hormones stimulating each side of metabolism

anabolism

conversion of smaller molecules into larger, complex molecules

examples of anabolism

-glucose becoming glycogen -- stored in liver
-fatty acids and glycerol become triglycerides -- stored in adipose cells
-amino acids become proteins
-insulin stimulates anabolism

catabolism

hydrolysis of molecules into subunits for use in cell respiration

examples of catabolism

glucagon stimulates catabolism of glycogen

how eating impacts blood glucose

rise in blood glucose; stimulate beta cells to secrete insulin and inhibit alpha cells from producing glucagon