MEDS 301 - Week 6 Endocrinolohy

Endocrine System

ductlesss glands influence a target organ by releasing hormones into the bloodstream

Hormones

substances produced within one organ and secreted directly into the circulation to exert its effects at a distant location

What are the eight endocrine glands?

pineal, pituitary, thyroid, thymus, adrenal, pancreas, ovary, testis

Pineal Gland(hormone+function)

secretes melatonin for sleep-wake cycle

Pituitary Gland(hormone+function+location)

anterior: growth-hormones, stimulating hormones

posterior: stores/releases oxytocin and antidiuretic hormone produced in the hypothalamus

Where is oxytocin and antidiuretic hormone produced vs. where is it released?

produced in the hypothalamus, stored and released in the posterior pituitary gland

Adrenal Gland(hormone+function)

Cortex: cortisol(metabolism+stress), Aldosterone(salt/water balance)

Medulla: Epinephrine and Norepinephrine(fight or flight)

Pancreas (hormone+function)

insulin(lowers blood sugar) and glucagon(raise blood sugar)

Hormone Classifications

By Mechanism: Lipid-soluble hormones, Water-soluble hormones

Lipid-Soluble Hormones

Diffuse through the target cell’s plasma membrane

require transport proteins in the blood

activate long-lasting gene expression changes

Water-soluble Hormones

are dependent on second messengers/surface receptors

dissolve in blood plasma

fast short-lived responses

Examples of lipid-soluble hormones

Steroids: androgens, cortisol, progesterone, estrogens

examples of water soluble hormones

Peptides and Amines: antidiuretic hormones, glucagon, insulin, somatostatin,

Hypothalamic-Pituitary Axis

hormones=human beings, glands=mob, pituitary=king, hypothalamus=god, brain=nonbeliever

human beings in a mob, whats a mob to a king, whats a king to a god, whats a god to a non believer

what are the lobes of the pituitary gland?

Anterior Lobe(Adenohypophysis), Posterior Lobe(Neurohypophysis)

What are the two types of hormone secretion

Positive Feedback, Negative Feedback

Positive Feedback

end product stimulates more production of the end product

Negative Feedback

end product inhibits production of the end product

What are the three layers of the Adrenal Cortex

Zona: Glomerulosa, Fasciculata, Reticularis

good friends ride

Zona Glomerulosa

Outermost layer of the adrenal gland

Releases mineralocorticoids/aldosterone

Regulates blood levels of sodium and potassium

Zona Fasciulata

Middle layer of the adrenal gland

Releases glucocorticoids/(Cortisol, cortisone)

regulates metabolism of carbs and proteins, and has anti-inflammatory effects

Zona Reticularis

Innermost layer of adrenal gland

Releases sex steroids

Normal physiologic function of the sex hormones from this layer not clearly understood

Functions of Glucocorticoids

causes gluconeogenesis and catabolism which regulates metabolism of carbs+proteins esp. during stress

also cause fluid retention

can restrict accumulate WBC at inflammatory sites

What are clinical implications of Glucocorticoids

inflammatory disorders, multiple sclerosis, hypercalcemia from cancer, adrenal corticol insufficiency, respiratory disease, management of leukemias and lymphomas

glucocorticoids do not cure but rather relieve symptoms

MoA of anti-inflammatory glucocorticoids

lipid-soluble hormone released into capillaries via transport globulins → diffuses out of vessel at target cell and diffuses through target cell membrane → bind to glucocorticoid receptors inside cytoplasm and translocate to nucleus → activated glucocorticoid receptors → binds to gene promotor region in genome and causes transcription of anti-inflammatory factors

Pancreatic islets

Pancreatic Endocrine Hormones

Glucagon and Insulin

Glucagon Secretion

increases circulating glucose levels by stim. gluconeogenesis in liver

helps conv. amino acids into glucose

Insulin actions

promotes cell use of glucose and carbohydrate storage

stims. glycogen synthesis in liver

facilitates entry of amino acids into the cell

Incretins

secreted by duodenal epithelial cells

stim. and inc insulin secretion

MoA of Glucose transporters and insulin release

glucose → GLUT2 → metabolized into ATP → depolarization occurs due to increase in ATP → K+ channels close, Ca2+ channels open → calcium influx triggers insulin+amylin release via exocytosis

Amylin

MoA of Insulin on cell

insulin binds to insulin recp on skeletal and heart muscle+adipose tissue → translocation of GLUT4 to plasma membrane to facilitate entry of glucose to cell

Other actions of insulin

insulin stims glycogen synthesis in muscle +liver and inhibits release of glucose from the liver into bloodstream

inhibits breakdown of protein and fat for energy while facilitating entry of amino acids for protein synthesis

Diabetes

disorder of pancreatic endocrine function causing

• deficient secretion of insulin

• insulin resistance

• combo of both

Types of Diabetes

Type 1 and Type 2

Type 1 Diabetes

Autoimmune disorder; destruction of beta cells, termination of insulin production

Type 2 Diabetes

Insulin resistance; obesity; genetic link

Symptoms of diabetes

increase blood glucose levels

glycosuria

polyuria

polydipsia

polyphagia

ketoacidosis

diabetic neuropathy

Management of diabetes

done via blood glucose monitoring

Treatment of Diabetes(immediate and preventative objective)

therapeutic objective:

• immediate: correct metabolic imbalance

• maintainance therapy: regulate blood glucose levels

  • diet control

  • exercise

  • medications

Drug classes use in treatment of diabetes

Parenteral

• insulins

• amylin anaglog

• incretin mimetics

Oral

• glucose absorption inhibitors

insulin adverse effects

shock

hypotension