Lecture 1- Introduction To Endocrinology Flashcards
Primary endocrine glands
Their main function is to secrete hormones e.g. pituitary, thyroid, adrenal glands and the pancreas
Secondary endocrine glands
Their main function is not to secrete hormones, but contain cells which to e.g. kidneys, stomach and liver
Exocrine glands
Secrete products into ducts that carry secretions unto body cavities, lumen of organ or to outer surface of body i.e. target organ
Endocrine hormone
Secrete hormones directly into the blood that act on distant cells
Paracrine hormone
Acts locally on neighbouring cells
Autocrine hormones
Acts on the same cell that secreted the hormone
Diurnal
Secreted daily
- cortisol is an example which is high in the morning and low at night
Melatonin
Secreted with a daily (circadian) rhythm
- secretion peaks at night
- controls sleep patterns
Positive feedback
Rate of process increased and product increases
E.g. oxytocin which stimulates and enhances labour contractions
Negative feedback
Rate of process decreased as the formation of the product increases
Acromegaly
Excess of growth hormone during adulthood
-symptoms include swollen hands/feet (squashed nerves = carpal tunnel syndrome); abnormal periods and erectile dysfunction; sleep apnoea
Down regulation
If a hormone is present in excess the number of target cells may decrease, decreasing sensitivity to hormone
Upregulation
If a hormone is deficient, the number of target cell receptors may increase, to increase sensitivity to hormone
Hypothyroidism
Low T3 and T4; high TSH
Hyperthyroidism
High T3 and T4; low TSH
Cushing’s syndrome
- Overproduction of ACTH from pituitary
- Overproduction of cortisol from the adrenal glands
Addison’s disease
Lack of cortisol and aldosterone
- due to autoimmune destruction of adrenal gland
- symptoms include weight loss; dizzy spells; hyperpigmentation due to build up to ACTH which stimulates production of melanin by melanocytes); frequent urination due to lack of aldosterone (less sodium reuptaken in the kidneys)
Cholesterol
Precursor to steroid hormones
Thyrotoxicosis
Excess thyroxine (T4) production
Hypoglycaemia
Insulin excess, low blood sugar
Insulin and cytokines act via which kind of receptor?
Intracellular (phosphorylation of intracellular proteins)
Steroid, thyroid hormones and vitamin D act via which type of receptor?
Intracellular (nuclear receptors)
Catecholamines, NO and peptide hormones act via which type of receptor?
Extracellular (g protein coupled receptors GPCRs)
What is the main action of intracellular receptors for hormones?
Phosphorylation of intracellular proteins
What is the main action of a GPCR leading to the specific hormone response?
Increase of intracellular cAMP
What is the effect to of insulin on glucose uptake?
Increased into fat and muscle
Hormone
A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action
Catecholamines
Water soluble e.g. adrenaline/ noradrenalin/ melatonin
Peptides
Water soluble e.g. insulin/ PTH
Steroids
Lipid soluble e.g. cortisol/ sex steroids/ vitamin D
Action of lipid soluble hormones
- Diffuses through the blood and plasma membrane into a cell
- Hormone binds to receptor in cystic or nucleus
- Alters gene expression
- Activates or suppresses the production of protein
Action of water soluble proteins
- Diffuses through blood and binds to receptor on exterior plasma membrane of target cell
- Hormone receptor compels activates the membrane protein (G protein)
- Activated G protein activates adenylyl cyclise
- This converts ATP to cAMP in the cystol (Ca 2+ is another secondary messenger)
- cAMP activates protein kinases (phosphorylates target cellular proteins)
- Produces physiological response- activation/suppression
- Phosphodiesterase deactivates cAMP
- Works with low concentration of hormone as second messenger causes cascade effect
Permissive effect
The response only occurs when there is a recent or simultaneous presence of a second hormone
Synergistic effect
Effect of two hormones acting together is greater than the sum of their individual effects
Antagonistic effect
When one hormone opposes the actions of another hormone
Gigantism
Caused by an adenoma (tumour of the pituitary gland)
- excessive growth hormone in children
- symptoms include large hands/feet; prominent jaw and forehead; flat nose/larger head/lips
What is insulin’s effect on glycogen?
Increase in glycogen synthesis
What is insulin’s effect on triglycerides?
Increase storage in adipose tissue
What is insulin’s effect on proteins?
Increased protein synthesis
What is insulin’s effect on the liver?
Decreases hepatic gluconeogenesis
What are the two main disorders associated with insulin deficiency?
Type I and type II diabetes
Excess insulin causes what condition?
Hypoglycaemia
Ghrelin
Increases food uptake
Where is ghrelin produced?
Stomach
