endocrine system

anatomy of endocrine system

1. brain

   1. hypothalamus

   2. pituitary gland

   3. pineal gland

2. thyroid and parathyroid glands

3. thymus gland

4. pancreas

5. adrenal glands

6. sexual organs

   1. testicle

   2. ovary

   3. placenta (during pregnancy)

what is the purpose of hormones

to maintain homeostasis

endocrine system sends signals to the body by secreting hormones into circulation:

1. chemical messengers

2. bind to specific receptors on target cells

3. feedback loops within the endocrine system regulate hormone levels in the blood stream

   1. trophic

   2. inhibitory

trophic feedback loop

tells gland to produce more of the hormone

inhibitory feedback loop

tells gland to produce less hormone

hormone deficiency syndromes

too little production

1. typically caused by an autoimmune disease

2. treatment is to replace native hormones orally (thyroxine, estradiol) or via injections (insulin, growth hormone)

hormone excess syndromes

too much production

1. typically caused by a tumor

2. treatment is more complex

where is the hypothalamus

base of the brain, below the thalamus and above the pituitary gland

what does the hypothalamus secrete

hormones that stimulate the pituitary gland to increase or decrease release of pituitary hormones

what does the hypothalamus regulate

body temperature, hunger, thirst, sleep and mood

where is the pituitary gland located

base of the skull, above optic chiasm

-2 lobes: anterior and posterior

what does the pituitary gland secrete

1. adrenocorticotrophic hormone→ adrenal glands

2. growth hormone → bones, muscles

3. prolactin→ mammary glands

4. thyroid secreting hormone → thyroid

5. follicle stimulating hormone (FSH) →testes and ovaries

6. luteinizing hormone → testes and ovaries

7. oxytocin → mammary ducts

8. antidiuretic hormone → kidney

what does the pituitary gland regulate

growth, metabolism, reproduction, stress response, water balance and lactation

growth hormone is essential for

normal growth and development in children and adolescents

-not essential for life in adult

when is the growth hormone activated

during times of high metabolic consumption (growth spurts)

growth hormone stimulates

the liver to produce insulin-like growth factor I (IGF-I) which prompts linear growth in bones and muscles

-highest growth in infancy and puberty

height follows

normal distribution

short stature

lower distribution of normal curve (proportional)

causes of short stature

1. growth hormone deficiency

2. intrauterine infections (rubella)

3. psychosocial dwarfism

4. renal failure in childhood

5. glucocorticoids given in childhood

treatment of short stature

injected growth hormone

achondroplastic dwarfism

limbs are disproportionally short (compared to head and trunk)

cause of achondroplastic dwarfism

inherited autosomal defect (fibroblast growth factor receptor 3)

treatment for achondroplastic dwarfism

none

tall stature

Higher distribution of normal curve ex: NBA player

-proportional growth

cause of tall stature

excessive growth hormone

gigantism

excessive growth hormone due to pituitary tumor

-disproportional limb length

gigantism adversely effects the body and results in decreased life expectancy causing

muscle weakness, cardiovascular disease, degenerative arthritis, visual deficits

antidiuretic hormone

helps body regulate body water by impacting reabsorption of water in the kidneys

water toxicity (exercise associated hyponatremia)

caused by excessive drinking of water or sports drinks

-exceeds kidneys ability to excrete excess water

-can occur in runners (13% marathon runners)

-results in life threatening hyponatremia

risk factors for water toxicity

long,slower paced events

symptoms of water toxicity

confusion, headache, weakness, dizziness, nausea, vomiting

in both dehydration and water toxicity

ADH levels are normal (not a problem with the hormone)

what is diabetes isipidus

NOT the same as diabetes mellitus

-ADH deficiency

symptom of diabetes insipidus

frequent urination

treatment for diabetes insipidus

increased water consumption and hormone replacement

syndrome of inappropriate antidiuretic hormone (SIADH)

excessive ADH

cause of syndrome of inappropriate ADH (SIADH)

tumors (small cell lung cancer)

pneumonia

head trauma

medication side effect

symptoms of SIADH

headache

nausea

vomiting

confusion

muscle cramps

weakness

treatment for SIADH

fluid restriction, medications, tumor resection

where is the pineal gland located

in the center of the brain, behind the thalamus (pinecone shape)

what does the pineal gland secrete

melatonin

what does the pineal gland (melatonin) regulate

sleep-wake cycles (circadian rhythms)

where is the thyroid gland

in the neck, inferior to the larynx

what does the thyroid gland secrete

thyroxine (T4)

what does the thyroid gland regulate

energy expenditure and thermogenesis (body heat and temperature)

thyroxines other effects on body

heart rate

cholesterol levels

glucose levels

hypothyroidism

very common! (common in infants 1/4000)

T4 deficiency

causes of hypothyroidism

Hashimoto’s disease (autoimmune disease more common in women)

iodine deficiency

thyroidectomy

thyroid ablation

medications (amiodarone→for afib)

symptoms of hypothyroidism (slows down)

cold intolerance

goiter (enlarged thyroid gland)

decreased energy (sluggish)

dry skin

muscle cramps

slowed mentation and speech

constipation

high cholesterol

higher glucose levels

-DOES NOT CAUSE OBESITY

treatment for hypothyroidism

oral T4 hormone replacement

hyperthyroidism

excessive T4

-burns muscle and bone leading to osteoporosis risk

-results in exophthalmos →bulging of eyeballs

causes of hyperthyroidism

grave’s disease (autoimmune disease)

tumors

symptoms of hyperthyroidism (speeds up)

weight loss

increased appetite

tachycardia

heat intolerance

diarrhea

tremors

treatment for hyperthyroidism

thyroidectomy

thyroid ablation

meds

radioiodine

-pts may need Beta blockers for tachycardia

where are the parathyroid glands located

posterior aspect of the thyroid gland

-4 glands

parathyroid glands secrete

parathyroid hormone

parathyroid glands regulate

calcium levels in the blood

parathyroid hormone is released by

the parathyroid gland in response to low calcium levels

3 actions of parathyroid hormone

1. stimulate bones to release calcium

2. increase absorption of calcium in the small intestine

   1. signal kidneys to reduce clearance of calcium

when calcium is normal, what does parathyroid hormone facilitate

formation of bone

calcium

essential mineral for bone health, synaptic transmission in the nervous system, and blood clotting

calcium travels in the blood bound to

albumin (50%) or freely (ionized)

99% of the body’s calcium is stored in ____

bones

calcium is absorbed through the ____

small intestine

-normal intake is 1000-1500 mg/day

vitamin D

absorbed from food (vitamin D2) and through photogenesis in the skin (vitamin D3/cholecalciferol)

-600-800 mg/day

vitamin D is converted to

calcitriol in the kidney

-increases calcium and phosphorus absorption in the intestinesV

Vitamin D plays a role in the

immune system

hyperparathyroidism

excessive PTH

-results in hypercalcemia →fragility fractures=fractures from low-energy trauma

cause for hyperparathyroidism

tumor

symptoms of hyperparathyroidism

dehydration, weight loss/anorexia, nausea, vomiting, polydipsia, pruritus

treatment for hyperparathyroidism

tumor resection, meds

hypoparathyroidism

PTH deficiency

-results in hypocalcemia

causes of hypoparathyroidism

removal of parathyroid glands, idiopathic

symptoms of hypoparathyroidism

numbness and tingling

cardiac arrhythmias

muscle spasm

confusion

treatment for hypoparathyroidism

increase dietary intake of calcium

vitamin D

calcitriol supplements

where is the thymus gland located

anterior mediastinum

the thymus gland secretes

thymosin

thymus gland regulates

stimulates lymphocyte maturation in the bone marrow, eliminates reactive t-cells preventing autoimmune diseases

myasthenia gravis

hyperplasia or tumor of the thymus gland

DiGeorge syndrome

hypoplastic or absent thymus gland

where are the adrenal glands located

retroperitoneal cavity superior to the kidneys

-fight or flight glands

-3 layers

adrenal glands secrete

cortisol

aldosterone

catecholamines (epi, NE, dopamine)

adrenal glands regulate

metabolism

blood pressure

immune system

body’s stress response

cortisol (hydrocortisone)

adrenocorticotrophic hormone (ACTH) from the pituitary gland stimulates the adrenal gland to release cortisol

-Stress hormone

cortisol fuels body by

influencing how the body uses carbs, fats, and proteins for energy

-increases glucose

other body effects of cortisol

increases BP

increases attention/memory

depresses the immune system

decreases pain

Cushing’s syndrome

excessive cortisol

-results in high BP and high blood sugar

causes for Cushing’s syndrome

tumor

glucocorticoid meds

symptoms of Cushing’s syndrome

weakness, fatigue, easy bruising, osteoporosis, pathologic fractures, fat deposition in cervical area (buffalo hump), red/round cheeks (moon face), abdominal striae, irritability

treatment for Cushing’s syndrome

tumor resection

meds

hormone replacement

Addison’s disease

cortisol deficiencyc

causes for Addison’s disease

autoimmune

fungal infection

HIV

TB

congenital adrenal enzyme defects

symptoms of Addison’s disease

weakness

fatigue

hypoglycemia

hyperpigmentation

hyponatremia

treatment for Addison’s disease

oral glucocorticoid meds

aldosterone- from adrenal gland

helps body hold onto water and sodium and excrete potassium

-Renin from the kidney stimulates the adrenal gland to release aldosterone (hypotension, hyperkalemia)

hyperaldosteronism

excessive aldosterone

-results in hypokalemia and hypertension

catecholamines -from adrenal gland

released by fight or flight response

-norepinephrine, epinephrine, and dopamine

-also found in sympathetic nervous system