Endocrine Physiology: Peripheral Hormones Flashcards
Thyroid gland
Largest pure endocrine gland
Follicles and areolar connective tissue
Produces 2 hormones = thyroid hormone (requires iodine) and calcitonin
Secretes thyroid hormone (thyroxine, TH, T3, T4) = acts on the cells
Increases metabolism
Increases heat
Major stimulus is being cold
Hyperthyroidism
Excessive thyroxine
Causes include tumour of thyroid gland
Symptoms = tachycardia, nervousness, hyperactivity, weight loss, hunger, hot, exophthalamus (bulgy eyes)
Graves’ disease
Hyperthyroidism
Autoimmune condition
Treatment = medication, radiation, surgery
Hypothyroidism
Low TH
Causes = autoimmune, low TSH, low iodine
Symptoms = cold and lethargic, weight gain, brittle hair and nails, mental sluggishness
Thyroid hormone replacement to treat
Cretinism
Low TH in first 2 years of life
Severe mental impairment
Low muscle tone
Sleepiness
Simple goiter
Enlargement of thyroid
Can be hypo or hyperthyroidism eg) low iodine or tumour
Asymptomatic until large = leads to dyspnea and dysphagia
Treatment = iodine in diet, surgery to decrease dysphagia (trouble swallowing) and dyspnea (trouble breathing)
Calcitonin
Secreted by thyroid gland Released if blood calcium levels are high Acts to decrease blood calcium Gut = decrease calcium absorption Kidney = increase calcium excretion Bones = increase calcium absorption
Parathyroid hormone
Secreted by parathyroid gland Antagonist to calcitonin Released if blood calcium is low Acts to increase blood calcium Gut = increase calcium absorption Kidney = decrease calcium excretion Bones = calcium released
Vitamin D
Activated by PTH
Stimulates calcium and PO4 3- absorption from intestine
Can be synthesized from cholesterol derivative when exposed to sunlight (via liver and kidney)
Vitamin D deficiency = children-rickets, adults-osteomalacia, decalcification of the bone, muscle weakness, weight loss, bone pain
Hyperparathyroidism
Hypercalcemia Kidney stones Bone weakness Hyperactivity of heart Treatment = surgery
Hypoparathyroidism
Decreased PTH Low blood calcium Irritability of muscles (tetany) Uncontrolled contractions in face and hands Treatment = vitamin D, calcium
Adrenal hormones
Medulla = epinephrine, longer sympathetic effect, increased heart rate, increased breathing rate, increased metabolism Cortex = steroids, mineralcorticoids = aldosterone, glucocorticoids = cortisol, androgens
Aldosterone
Released if blood volume or sodium is low (or potassium is high)
Acts on renal tubules in kidney = speeds up sodium/potassium pump, increase sodium reabsorption, increase water reabsorption
Also part of the RAAS system = plays a role in blood pressure control
Cortisol
Glucocorticoid Plays a role in glucose balance Increases blood glucose Stimulates hepatic gluconeogenesis Inhibits glucose uptake by the cells Stimulates protein breakdown in muscle Facilitates lipolysis “Stress hormone” = high blood glucose and fatty acids, plays key role in adaptation to stress Anti-inflammatory and immunosuppressive effects, can result in sickness if cortisol is high
Androgens
Secretes both male and female sex hormones in both sexes
Males produce estrogen
Females produce testosterone
Dehydroepiandrosterone (DHEA) = overpowered by testicular testosterone in males, physiologically significant in females = pubic and axillary hair, pubertal growth spurt, female sex drive
Hyperadrenalism
Increase adrenal cortex hormones
Conns syndrome
Increase aldosterone
Increase blood pressure
Cushing’s syndrome
Increase cortisol Hyperglycaemia Hyperlipidemia Poor immune function Weight gain Sweating
Hypoadrenalism
Addison’s disease Decrease adrenal hormones Weight loss Nausea Muscle weakness Low blood pressure Hormone replacement
Androgenital syndrome
Adrenal disorder
Increase sex hormones
Symptoms in adult females = hirsutism (hair), deep voice, muscular arms/legs, breasts smaller and menstruation may cease
Newborn females = have male type external genitalia
Prepubertal males = precocious pseudopuberty
Adult males = has no apparent effect
Pheochromocytoma
Tumour of adrenal medulla Increase epinephrine and norepinephrine Ages 30-60 Symptoms = palpations, increase blood pressure, rapid heart rate, weight loss Treatment = surgery
Pancreas
Exocrine cells (acinar cells, secrete digestive enzymes) Endocrine cells (pancreatic islets, islets of langerhans, ~1 million) Alpha cells (15%, glucagon) Beta cells (80%, insulin) Delta cells (5%, secretes somatostatin, inhibits secretion of insulin and glucagon)
Insulin
Released when blood glucose is high Causes glucose to move into the cells Decreases blood glucose Glycogen formation Also promotes cellular uptake (fatty acids, amino acids, enhances their conversion triglycerides and proteins)
Glucagon
Released if blood glucose is low
Acts to increase blood glucose by gluconeogenesis and glycogenolysis (break down of glycogen) and ketogenesis
