Year 1: Endocrinology Flashcards
endocrine gland
group of cells which secrete messenger molecules directly into blood
neurotransmitters
chemical signal which transmits informtation over a chemical synapse (from neuron to other target cell)
List the three classification groups of hormones
Polypeptide/ Protein Hormones
Steroid Hormones
Miscellaneous Hormones (don´t fit into either category)
Synthesis of Protein Hormones
Via Gene expression:
- pro hormone mRNA
- translation of rough ER
- transfered to Golgi for Processing
–> Packed into vesicles with enzyme to cleave pro-hormone (activation)
Synthesis of Steroid Hormones
- all derive from cholesterol (stored in vesicles in cell)
- released by Esterase
- transport into Mitochondria (StAR - protein) (often rate-limiting step)
processing by enzymes in mitochondria
Storage of Protein Hormones
Stored in Vesicles in Cells until secretion
Storage of Steroid Hormones
- Stored in Blood
–> Bind to Plasma protein (e.g. Albumin (binds all steroid hormones) or specific plasma protein + some free hormones:
forms equilibrium: free hormones + free plasma protein = plasma bound protein
Receptors /direct effect of protein Hormones
G-protein coupled receptors
- bind to receptors and all modify cell signaling
(e. g. cAMP production, drives cholesterol production)
Receptos / direct effect of steroid hormones on cell
diffuse into cell (no membrane-boudn receptors required)
–> bind to intracellular target (receptor)
–> travel into nucleus with complex and regulate transcription
Positive feedback
A increases which causes B to increase which causes A to increase ( exponential growth, rather unstable)
Negative feedback
Negative feedback: secretion and production of hormone is controlled by released product (high concentration of product = low production /secretion of hormone)
–> controll of hormones (gives stability)
Location of hypophysis
beneath hypothalamus
in sella turcica
Hypothalmic nucleus
collection of neural cell bodies in hypothalamus
List Five (Six) Hormones produced by Adenohypophysis
Somatotrophin
Prolactin
Thyroid stimmulating Hormone (TSH, THyrotrophin)
Luteinsing Hormone (LH), Follicle Stimmulating Hormone (FSH)
Adenocorticotrophic Hormone (ACTH, Corticotrophin)
Somatrophin (cells, Hopothalamic Hormones, Effect)
Cells: Somotrophs
Hypothalamic Hormones: up: Growth Hormone / Somatrophin releasing Hormone (GHRH); down: Somatostatin
Effect:
growth: direct (on cells) indirect (on liver –> IGF 1)
– increased metabolism (protein synthesis, gluconeogenesis, fatty acid production, cartilage + somatic cell growth)
Prolactin (cells, Hypothalamic Hormones, Effect)
Cells: Lactotrophs
Hypothalamic Hormones: down (constant) Dopamine
up: Thyrotropin-releasing hormone (TRH)
Effect:
Mild production (suppression of Dopamine)
Control of Somatotrophin
Stimmuli on Hypothalamus: Sleep, oestrogen, stress, fasting, Gherline (from stomach))
Negative feedback:
IGF on Hypothalamus and Adenohyoophysis
Somatotrophin (GH) on Hypothalamus
Control of Prolactine
Stimmulus: Suckling on Breast + TRH
Suppression of Dopamineproduction by Hypothalamus
–> Milk secretion
Thyroid Stimmulating Hormone (cells, hypothalamic hormones, effect)
Cells: Thyrotrophs
Hormones: up: TRH (Thyrotrpin Releasing Hormone)
Effect:
On Thyroid
LH and FSH (cells, hypothalamic hormones, effect)
Cells: Gonadotrophs
Hormones: Gonadotrophin releasing hormone (GnRH)
Effect:
Ovaries and Testicles
Adenocorticotrphic hormone (ACTH) (cells, hypothalamic hormones, effect)
Cells: Corticotrophs
Hormones: UP: Cocticotrophin releasing hormone, Vasopressin
Effect:
Adrenal cortex
Median eminence
Area which connects adenohypohysis with neurones,
Many blood vessels
Magnocellular neurones
terminate in neurohypohysis
(cell bodies both in paraventricular and supraoptic nuclei found)
Parvocellular neurones
terminate in either median eminence or other part of brain
(cell bodies only found in paraventricular nuclei)
Supraoptic neurons
Go from Supraoptic nuclei to Neurohypophysis (Magnocellular neurons)
Store Hormones in Herring bodies
Either produce Vasopressin or Oxytocin
Paraventricular neurons
derive from paraventricular neucleus to neurohypohysis (Magnocellular neurones, majority) or other parts + median eminence (parvocellular neurones)
Produce either vasopressin or oxytocin
Structural difference vasopressin, oxytocin
2AA differ
Synthesis of Vasopressin and Oxytocin
Pre-Prohormone (with Signaling peptide)
–> Prohormone (cleavage for activation:
Vasopressin+Neurophysin+Glycopeptide
Oxytocin + Neurophysin (slightly different)
Compare differnet receptors for vasopressin
- V1: in atherial smooth muscle + adenohypophysis (ACTH production)
- linked to G-protein + phospholypase C (up: Ca2+, IP3, DAG in cell) –> Vasoconstriction
- V2: water reabsorbtion in duct cells (antidiuretic effect)
- linked to G-Protein and cAMP production –> induces travel of Aquapoins (AQP2) to lumen of kidney
Feddback control for Vasopressin
Stimmuli: Plasma osmolarity up (reabsorbtio of water required)
BP down ( vasoconstriction required, a bit less relevant)
Polydipsia
inceased thirst
Polyuria
increased volume of urine
Disregulatin of Vasopressin
Diabetis insipidus:
No reuptake /little reabsorbtion of water
–> polydipsia + polyuria
Central/cranial = no VP produced
Nephrogenic = resistance to VP
Summarise the effects of Oxytocin on several organ systems
On Uterus
- contraction of myometrial cells in uterus –> delivery of baby (+ encanced productio of prostoglandins which make cervix softer + dilate)
On Mammary glands:
- Contracti on of myoepithelial cells –> Milk ejection (no milk production)
CNS: Tend and Befriend
Other effects: temporary vasodilaition, vasoconstriction of umbilicus, on kideny: Vasopressin -like effects
Regulatio of Oxytocin
Dysregulation of Oxytocin
No / too little milk ejection
induction of labout might be required
Which factors (Hormones) regulate Blood glucose level? (Feedback Loop)
It is controlled via blood glucose levels:
Down: Insulin
Up: Glucagon, Cortisol, Somatotrophin, Catecholamines
How gets glucose into cells?(and effect of insulin on it)
Via GLUT-4, Insulin enhanced Glucose transporter (7times higher with Insulin)
Islets of Langerhans
2% of pancreatic tissue
a,ß, delta cells
paracrine regulation
gap junctions allow small molecules to pass, tight junctions allow small intercellular spaces to form
a- pancreatic cells
secrete Glucagon
pancreatic ß cells
secrete insulin
pancreatic delta cells
secrete somatostatin
Synthesis of Insulin
Synthesis of pre-pro insulin
–> cleaved: proInsulin + C-peptide (secreted 1:1 into blood)
posttranslational modification:
Insulin (two chains, connected through disulfide bonds)
When is insulin secreted?
What effects does insulin have?
When is Glucagon Secreted?
What are the effects?
+ Proteolysis
+ ketone body production
What is the Incretine effect? How is is achived?
More insulin is secreted after a meal compared to IV glucose
–> Glucagon-Like-Peptide (GLP1)
–> promotes insulin, supresses glucagon
DM type 1: patophysiology and clinical features
Diabetes Type 1:
Insulin deficiency because of autoimmune reaction to ß-cells
- proteolysis and weight loss
- Hyperglycaemia
- Polydipsia, Polyuria
- Ketouria
DM type 2: patophysiology and clinical features
Insuline resistance:
–> no problem with receptors! –> insulin as growth hormone still works, but no metabolic activity
60-80% OBESE.
* Dyslipidaemia (abnormal fat content in blood)
* Later insulin deficiency (exhaustion of beta cells).
* Hyperglycaemia.
* Fewer osmotic symptoms.
* T2DM presents with complications whereas T1DM hardly ever presents with complications.
–> resides in liver, muscle and adipose tissue
Explain relationship between dyslipidemia, hypertension and insulin resistance
dyslipidemia: hypertension in LDL which is associated with Ischaemic heart disease and atherosclerosis –> hypertension
No insulin= no uptake of triglycerides into cell but only release –> free fatty acids (mainly LDL)
Metabolic effects of insulin resistance
increase in NEFA (non-essential fatty acids), tryglycerides, LDL cholesterol
- decrease in: HDL, lipoprotein lipase activity, VLDL clearance
–> enough insulin present to suppress proteolysis and ketone production –> no ketones in urine and no weight loss
Explaint the Anatomy of thyroid gland and a thyroid follicle
Basal metabolic rate
Grundumsatz
Explain the Synthesis of thyroid hormones
Explain Mechanism of action of thyroid hormones
T4 gets into T3
–> stimulation of Protein synthesis via binding toTHR (Thyroid hormone receptor) in nucleus
+ less important: T3 non-nuclear actions on ion-channels
+ metabolic stimulation of cell
Actions/Effect of Thyroid hormones
fetal growth and development
- increases basal metabolic rate –> carbohydrate, fat and protein metabolism
- potential increase of catecholamines –> adrenaline, dopamine etc. –> increases heart rate, lipolysis etc.
- also effects on GI, CNS and reproductive symptoms
Control of TH production
Wolff-Chaikoff- Effect
Iodine inhibits release of Thyroid horomones (for about 17 days)
Where does the thyroid gland originates from?
back of tounge (thyro glossal dot) (average ca. 20g)
What is the foramen caecum of the tounge?
Little dot at apex of tounge due to thyroid development (disappearing thyroid duct)
Anatomy of the thyroid
Weight: 20g
Three possible problems with thyroid
Agenisis (no formation)
Incomplete descent (e.g. Lingual thyroid)
Thyroglossal cyst
Effects of Agenesis of thyroid (or total lack of thyroxin)
Cretin:
- irreversible brain damage bc of lack of thyroxin
Treatment/ prevention: Life-long replacement
Simple thyroxin sinthesis diagram
Compare thyroglobulin and thyroxin binding globulin
Thyroglobulin: protein in colloid of follicular cell , storage of thyroxin
Thyroxin binding globulin TBG: protein in blood that binds to Thyroxine in blood ( 75% bind, 1% free)