Endocrinology Flashcards
Endocrine Hormones
Adrenaline - Fast Acting, GPCR
Growth Hormones - Slow TKLR
The same hormone can have different effects on different cells via specific receptors.
Have an effect on low concentrations
Action terminated via -ve feedback loop
Autocrine Chemicals
Cytokines
Act within the same cell which they were synthesised
Paracrine Chemicals
Histamine
Act local to the synthesis - Diffuse through ECF
Exocrine Chemicals
Act through ducts of exocrine glands to external environment. eg. Glands
Insulin
Increases/Decreases Gluconeogenesis in Liver
Increases uptake of Glucose in skeletal muscle/adipose
Types of Endocrine Hormones
Peptide/Protein - Amino Acids
Steroids - Cholesterol
Amines - 2 AA Tyrosine, Tryptophan
Peptide Hormone Synthesis
Preprohormone - Synthesised by Ribosomes
Cleaved in RER to Prohormone
Prohormones are packed into vesicles with proteolytic enzymes into Golgi Apparatus where broken into Hormones and fragments stored in Endocrine cells
Measuring inactive fragments in plasma can be useful clinically e.g. C-peptide (insulin) in diabetes
Steroids Hormone Synthesis and transport
Highly Lipophilic - Synthesised When needed
Carried through ISF by binding to carrier proteins such as Albumin protects from enzymatic degradation. Carriers can also be specific
eg. corticosteroid binding to globulin
receptors are located inside cells (cytoplasmic or nuclear receptors) and trigger either activation or repression (inhibition) of gene function within the nucleus = genomic effect.
Increasing / Decreasing protein synthesis
Permissive Effect of Hormones
Thyroid Hormone doesn’t have an effect on its own to lipolysis but it has an additive effect to the function of epinephrine. Together causing a greater effect than the one epinephrine would have by itself
Short Half Life Hormones
Catecholamines and Peptide Hormones
Excreted through kidneys and liver
Non-tropic hormones
Tropic hormones
Hormones directly stimulate target cells - PP - Blood
Act on another endocrine gland - AP - Capillaries
Pituitary Hormones and their targets
Tropic
FSH + LH - Testes/Ovaries
TSH - Thyroid
ACTH - Adrenal Cortex
Non Tropic
MSH - Melanocytes
Prolactin - Mammary Glands
GH - Liver, Bones (Non Tropic + Tropic)
How is the hypothalamus connected to posterior pituitary gland
Infundibulum
Anterior Pituitary Hormones
All Tropic (control secretion of other endocrine glands) Except Prolactin
Thyroid Stimulating Hormone (TSH) - thyrotropin Adrenocorticotrophic Hormone (ACTH) - corticotropin
Gonadotropins Follicle Stimulating Hormone (FSH) Luteinising Hormone (LH) Growth Hormone (GH)
Prolactin directly stimulates milk production from the breast during lactation
short Feedback loop
long Feedback loop
direct feedback from physiological response
anterior pituitary to hypothalamus
endocrine target cell upwards
PTH (independent of pituitary control).
Leptin
Peptide hormone released by fat stores which depresses feeding activity
Normal range of [BG] =
Hypoglycaemia =
4.2-6.3mM (80-120mg/dl)
[BG] < 3mM olic
Enterokinase
converts trypsinogen to trypsin
Proteases Nucleases Elastases Phospholipases Lipases α-Amylase
Cleave peptide bonds Hydrolyse DNA/RNA Collagen digestion Phospholipids to fatty acids Triglycerides to fatty acids+ glycerol Starch to maltose + glucose
4 types of islet cells in Pancreas + Functions
A cells produce GLUCAGON
B cells produce INSULIN
Delta cells produce SOMATOSTATIN (slows down absorption to prevent exaggerated plasma peaks)
F cells produce pancreatic polypeptide
may help control of nutrient absorption from GIT
Insulin
Increase Oxydation
Decrease BG - G taken up by cells
Increases Glycogen synthesis in muscle and liver. Stimulates glycogen synthase and inhibits glycogen phosphorylase.
Inhibits the enzymes of gluconeogenesis in the liver
Increases amino acid uptake into muscle, promoting protein synthesis. Inhibits proteolysis
Increases triacylglycerol synthesis in adipocytes and liver i.e. stimulates lipogenesis and inhibits lipolysis.
Has a permissive effect on Growth Hormone
Promotes K+ ion entry into cells by stimulating Na+/K+ ATPase.
GLUT-1, GLUT-3
GLUT-2
GLUT-4
Basal glucose uptake in many tissues
eg. Brain, Kidney and RBC’s
B-cells of pancreas and liver (NOT insulin dependent)
*Glucose conv. to G6P by hexokinase keeping ICG low
Muscle and Adipose Tissue ONLY tissues which are insulin sensitive
Stimuli which increase insulin release
- Increased [BG]
- Increased [amino acids] plasma
- Glucagon (stimulates insulin to take up glucose created via gluconeogenesis)
- Incretin hormones controlling GI secretion and motility eg. gastrin, secretin, CCK, GLP-1, GIP.
- Vagal nerve activity
Stimuli which inhibit insulin release
- Low [BG]
- Somatostatin (GHIH)
- Sympathetic a2 effects
- Stress e.g. hypoxia
Stimuli that promote glucagon release
Low [BG]
*High [amino acids]. Prevents hypoglycaemia following insulin release in response to aa
Sympathetic and epinephrine, b2 effect, Cortisol
Stress e.g. exercise, infection
Stimuli that inhibit glucagon release
Glucose
Free fatty acids (FFA) (Lipolysis) and Ketones
Insulin
Somatostatin
DMT2 Treatment
Restore insulin sensitivity of tissues with exercise and dietary change
Oral hypoglycaemic drugs eg. Metformin (inhibits hepatic gluconeogenesis and antagonises glucagon)
Sulphonylureas act by closing the K ATP in b cells and
stimulating Ca2+ entry and insulin secretion
90 mg/dl to mM
900 mg/L
/180 mM = 5
90 mg/dl / 18 = 5
Development of Type 1 Diabetes
Genetic Predisposition plus
Trigger (Viral Infection) /
Auto-Immunity (HLA) - Auto-digestion
Autoimmune attack on islet cells – lymphocyte infiltration of islets (insulitis) – destruction of B cells
Insulin controls intracellular processes
ADIPOSE TISSUE - Reduced lipolysis
LIVER - Reduced glucose production
MUSCLE - Increased glucose uptake
Type 1 DM
Signs
Ketones on breath Dehydration Increased respiratory rate, tachycardia, hypotension. Low grade infections, thrush / balanitis Linked to other Autoimmune Diseases
Type 1 DM
Symptoms
Thirst Tiredness Polyuria / Nocturia Weight loss Blurred vision Abdominal pain
Type 2 DM
Signs
Not ketotic, May have NO Symptoms
*Usually overweight but not always
Low grade infections, thrush / balanitis
*May have micro vascular or macrovascular Cx
DM Screening Risk Factors
Overweight
Family history
Over age 30 years if Maori ⁄ Asian
Over age 40 years if European
History of Gestational Diabetes
Had a big baby (more than 4 kg)
Inactive lifestyle, lack of exercise
Previous high blood glucose