Hormones Flashcards
What are types of communications in the body
Endocrine Paracrine Autocrine Exocrine Neural Neuroendocrine
How does endocrine hormone work
Carried in blood to the target organ
If no receptor = no response
Receptors have high affinity for hormone
How is action terminated
-ve feedback loop
How do paracrine hormone work
Acts local to site of synthesis e.g. histamine
How do autocrine hormones work
Act on or in the same cell that synthesises e.g. cytokine
How do exocrine hormones work
Released from exocrine glands via ducts into the blood
How do nerves transmit information
Neuotransmitter released from pre-synaptic neuron
Travels across synaptic cleft to post synaptic cell
Acts locally
How do neuroendocrine hormones work
Hormone released by nerves into blood NOT synaptic cleft
What are the different types of endocrine hormone
Peptide
Steroid
Amine
What is most common hormone and what is it composed off
Peptide hormone
Composed of chains of AA
What are steroid hormones composed off and give example
Lipids composed of cholesterol
Oestrogen / progesterone
What are amine hormones composed of and what hormones are produced
Amino acid - tryptophan + tyrosine
Tryptophan makes melatonin
Tyrosine makes all others
How are peptide hormones produced
Synthesised in ribosome and stored in vesicle in gland as pre-prohormone (large and inactive)
Cleaved in RER to form prohormone = inactive
Packaged into vesicles with proteolytic enzyme in Golgi
Broken down into active hormone + other fragments which are stored till release is triggered
What can be used clinically to measure work of gland and give example
Can measure inactive fragment as stay in plasma for longer e.g. C-peptide in DM will indicate endogenous insulin from pancreas
What is the mechanism of action of peptide hormones
Hydrophillic
Dissolve in plasma
Can’t cross membrane so bind to target cell receptor s to initiate a response
How does binding activate a response
GPCR pathway - activate 2nd messenger system / ion channel to modify existing protein = rapid response
Tyrosine kinase pathway - altered gene expression giving slower but longer lasting response
Opens or closes channels = hyper or depolarisation
When are steroid hormones synthesised
As needed
How are steroids produced
Production from chlesterol
Diff enzymes = different product
What enzyme is required to make cortisol and aldosterone
21 hydroxylase enzyme
If deficient = adrenal hypoplasia
What is a pre-hormone of androgens which declines with age
DHEA
What is the mechanism of action of steroid
Highly lipophilic so cannot be retained in lipid membrane
Poorly soluble do transported with carrier protein such as albumin
Only unbound hormones can diffuse into target cell
Where are sex steroids produced
Gonads
Where is Vit D3 produced
Kidney
Where are mineral and glucocorticosteroids produced
Adrenal cortex
What is the mechanism of action of steroid hormones
Cross plasma membrane easily
Receptors inside cell activate to repress gene function leading to increase or decrease in protein synthesis
Some bind to membrane receptors and activate via 2 messenger
Lag between hormone release and effect but persists
Why do steroids make good anti-inflammatory
Switch off proteins that code for inflammation
What are examples of amine hormone
Catecholamine
Thyroid (T3+T4)
Melatonin
What mechanism of action to catecholamine’s have
Similar to peptide
HYdrophillic
Examples of catecholamines and where are they released from
Dopamine - brain
Noradrenaline - neurones
Adrenaline - adrenal medulla
What mechanism of action to thyroid hormones have
Steroid
What do they bind too
Thyroxine binding globulin
What factors impact on endocrine function
Negative feedback Neuronal feedback Up regulation Down regulation Antagonism Permissive
What is an example of neuronal feedback
Sympathetic system triggers adrenal medulla to release adrenaline
What is up regulation
After exposure to low hormone get increased number of receptors and increased tissue sensitivity
What is an example of antagonism
Too much GH = reduced number of insulin receptors so present with DM
What is an example of permissive
Presence of one hormone enhances another
Thyroid increases receptors for epinephrine = increased lipolysis
Insulin increases GH
What is required for monitoring hormones
24 hours as levels fluctuates
What is the stress response
Hypothalamic and pituitary axis activated
Sympathetic nervous system activated
Failure of normal feedback mechanisms
What else happens
Na and water retention
Suppression of anabolism
Muscle protein loss
What does sympathetic do in stress
Stimulate catecholamine
Get tachycardia and hypertension
What hormones are increased in the stress response
GH Cortisol Renin Aldosterone Prolactin ADH Glucagon
What hormones are decreased in the stress response
Insulin
Testosterone / oestrogen
What hormones have no change
TSH / LH / FH
Typical features of thyrotoxicosis
Hair loss
Pretibial myxoedema
Onchylysis
Bulging eyes - exophthalmos / proptosis
Typical features of hypothyroid
Hair loss
Cold
Pale skin
Typical features of Cushing’s
Central obesity Wasted limbs Moon face Buffalo hump Striae
Typical features of Addison’s
Hyperpigmentation
Typical features of Acromegaly
Soft tissue overgrowth Big jaw (macrognathia) Big hands and feet Thick skin Coarse facial features
Typical features of hyperandrogism
Hirsutism
Temporal balding
Acne
Typical features of hypopituitarism
Pale or yellow thin skin
Fine wrinkling around eyes and mouth
Hypoparathyroid
Dry scaly puffy skin
Brittle nails
Coarse hair
Pseudohypoparathyroid
Short stature
Short neck
Short 4th+5th metacarpals
If want to test for excess hormone what do you do
Try to suppress
If can’t suppress = autonomous secretion
If want to test for deficiency what do you do
Try to stimulate
If can’t produce then found the issue
