Define a hormone?
Blood borne chemical mediator released from endocrine glands that act on distant cells
Describe the major differences between the nervous system and the endocrine system?
How many hormones can be produced by one endocrine gland?
How many glands can one hormone be produced by?
Glands may produce multiple hormones
Multiple glands may produce one hormone
What is a neurohormone?
What are the three major groups?
A neurocrine secreted into the bloodstream
3 major groups:
Hypothalamus > anterior pituitary
Hypothalamus > posterior pituitary
What is the difference between tropic and trophic hormones?
Tropic hormones control the secretion of another hormone
Trophic hormones stimulate growth and development
How are tropic hormones usually named?
Usually have names that end in 'tropin'
Describe the different ways by which hormones can be classified?
Source of hormone
Hormone structure (peptide, amine, steroidP
Hormone solubility (hydrophilic or lipophilic)
Binding of receptor type
Describe the differences between peptide, steroid and amine hormones?
Describe the difference in synthesis and storage between peptide, steroid and amine hormones?
Peptide: made in advance, stored in secretory vesicles
Steroid: synthesised on demand from precursors
Catecholamines: made in advance, stored in secretory vesicles
Thyroid hormones: made in advance, precursor stored in secretory vesicles
Describe the difference in release mechanism between peptide, steroid and amine hormones?
Describe the reason for each mechanism.
Peptide: exocytosis (lipophobic)
Steroid: simple diffusion (lipophilic)
Catecholamines: exocytosis (lipophobic)
Thyroid hormones: simple diffusion (lipophilic)
Describe the difference in transport in the blood between peptide, steroid and amine hormones?
Peptide: dissolved in plasma
Steroid: bound to carrier proteins
Catecholamines: dissolved in plasma
Thyroid hormones: bound to carrier proteins
Describe the half-lives of peptide, steroid and amine hormones?
Thyroid hormones: long
Describe the location of receptors for peptide, steroid and amine hormones?
Explain the reason for each.
Peptide: cell membrane (lipophobic)
Steroid: cytoplasm or nucleus (lipophilic)
Catecholamines: cell membrane (lipophobic)
Thyroid hormones: nucleus (lipophilic)
Describe the response to receptor-ligand binding in peptide, steroid and amine hormones?
Peptide: activation of second messenger systems (membrane receptor)
Steroid: activation of genes for transcription and translation (cytoplasmic/nuclear receptors)
Catecholamines: activation of second messenger systems (membrane receptor)
Thyroid hormones: activation of genes for transcription and translation (nuclear receptors)
Give examples of peptide, steroid and amine hormones?
Peptide: insulin, PTH
Steroid: oestrogen, cortisol
Catecholamine: adrenaline, noradrenaline
Thyroid hormones: thyroxine
Briefly describe the process of peptide hormone synthesis?
Preprohormone synthesised by ribosomes > ER lumen > cleaved to prohormone > Golgi complex > secretory vesicles with prohormone formed > enzymes cleave into active hormone > exocytosis
What is the parent compound for all steroid hormones?
Describe the action of steroid and thyroid hormones after receptor binding?
Alter gene expression and produce new proteins
Describe the influences on plasma hormone concentration?
Rate of secretion by endocrine gland
Rate of metabolic activation
Extent of binding to plasma proteins
Rate of metabolic inactivation and excretion
Describe the different mechanisms of hormone removal?
Steroid: conjugation > urine and bile
Amines: circulating degrading enzymes
Large peptides: receptor-mediated endocytosis
Small peptides: kidneys
Describe the different mechanisms of regulation of hormones secretion?
Negative feedback systems: long loops and short loops
Positive feedback systems
Diurnal and circadian rhythms
How is regulation of cortisol release achieved?
According to diurnal and circadian rhythm
Describe permissive regulation of hormone secretion?
First hormone cannot exert its effects without presence of second hormone
eg. cortisol and adrenaline
Describe the difference between a primary and secondary endocrine disorder?
Primary: abnormal endocrine gland
Secondary: normal endocrine gland, something wrong elsewhere in pathway
List some possible causes of decreased or increased hormone activity?
DECREASED: hyposecretion, increased removal from blood, lack of receptors, lack of enzyme for cell response
INCREASED: hypersecretion, decreased plasma protein binding, dcreased removal from blood
Describe the general approach to treatment for decreased and increased hormone activity?
Decreased: hormone administration
Increased: tumour removal, inhbiting drugs