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)
Pimary hypothyroism (cause, effects, symptoms)
-Primary thyroid failure (myxoedema)
damage = autoimmune
Up: TSH, down: T3+T4
Symptoms
- fatigue,
- cold intolerance
- depression
- weight gain
- less appetite
- bradycardia
- costipation (verstopfung) –> a lot because of decrease of basal metabolic rate + no help in catecholamides
–> eventually
myxoedemal coma
Hyperthyroidism symptoms + reason
Autoimmune –> antibodies stimmulate TSH receptors on thyroid
- inceased basal metablic rate:
- raised temperature,
- increased appetide,
- weight loss,
- tachycardia,
- myopathy,
- mood swings,
- tiredness,
- diarrhea,
- tremor of hands
Graves Disease
Autoimmune disease
Symptomps of hyperthyroidism
+ Sore + swollen eyes –> 2nd antibodies on eye
non-pitiing ptetibial myxoedema –> growth of soft tissue in ankle region (3rd. antibodies)
Anatomy of Adrenals
Medulla =produces catecholamines (e.g.adrenaline)
Cortex –> produces cortecosteroids (e.g. aldosterone, cortisol* sex steroids)
Which Zones in Adrenals produce which hormones?
Binding of the two hormones in blood
Glucocorticoid + mineralcorticoid
+ Medulla = catecholamides
Glucocorticoid: colesterole (only 10 % free)
Mineralcorticoid: Aldosterone (45% free)
To which receptors do Aldosterone and Cortisol bind?
Aldosterone: Bind to Mineralcorticoid receptors
Cortisol Bind to Glucocorticoid receptors + Mineralcorticoid receptors
–> some tissues are prodected from cortisol by 11bhsd2 so aldosterone has a task to do (Kidney + Placenta)
When is aldosterone secreted?
Angiotensinogin —Renin—> Angiotensin 1
(Renin : low BP, low Na2+, sympathetic renal activity)
Angiotensin 1 —ACE—> Angiotensin 2
Angiotensin 2 –> stimulates Aldosterone secretion (can be also stimulated by low Na+ and high K+ but to a lesser extent)
Effects of Aldosterone + Mechanism of action
Effect on Kidney (collecting duct)
-> reabsorbtion of Na2+ (Transcrtiption of proteins: sodium chanel formation + Na2+/K+ ATPase active pump of Na2+ into blood –> loss of potassium)
Feedback control of cortisol
Mechanism of Action of Cortisol + effects
highly binds to MR, Partly binds to GR
Metabolic actions: central glucose availability and storage
up: gluconeogenesis, glycogenesis
down: peripheral glucose storages, uptake of fatty acids in skeletal muscleand fat tissue, reduction of blood flow in these tissues)
Memory: pro memory (up: serotonin receptors) (down for supraphysological effects)
Immune: Anti-inflammatory and immunosupressive
Addisons disease (cause, clinical features, management)
Primary adrenal failure –> lack of cortisol
Causes
- autoimmune desease damages adrenal cortex
- TB of adrenal gonads
Features
- Tanning (A lot of ACTH released –> hypothalamus wants to make more Cortisol –> POMC is cleaved into ACTH and MSH (Melanocyte stimulating hormone)
- Salt loss (low sodium, high potassium levels)
- Hypotonic
- weight loss, decreased appetite
- fatigue
Management
- IV saline for rehydration and sodium intake
- IV glucose
- oral steroid hormone replacements
Cushing`s syndrome (causes + features)
High cholesterol levels
Causes
- Oral replacement /intake of steroid hormones
- Pituitary adenoma(Cushing`s disease)
- Adrenal adenoma/carcinoma
- Ectopic ACTH (lung cancer)
Clinical features
- diabetes (long times of high blood glucose levels)
- weight gain (redistribution: central weight, thin legs and arms, excessive nuchal fat, moon face)
- Skin (acne, facial hair, thin, easy bruise, striae (stretch marks))
- proximal myopathy –> reduction of protein and muscle + osteoporosis
- depression
- hypertension
- immunosupression (poor wound healing, reactivation of TB)
Conn’s syndrome
Cause:Aldosterone Adenoma
Features:
Hypertension
Oedema
high Na+, Low K+
Primary + secondary amenorrhoea
Primary amenorrhoea:
never had period
Secondary amenorrhoea:
have had normal periods, but don’t have it anymore
Oogenesis
gametogenesis in females
oogonia “freezed” untill puberty
Spermatogenesis
begins at puberty
Hypothalamo-Pituitary-Testicle Axis
FSH: gametogenesis
LH: hormone production
Describe the main Main structures in testis from spermatogenesis to urethra
1. Coiles seminiferous tubules (spermatogenesis)
- -> formes tubules –> Seitoli cells (Spermatogenesis; FSH sensitive)
2. Rete testis and Vasa efferentia –> connect coiles siminiferous and vas dererens
3. Epididymis (storage of sperms)
4. Vas deferens (to urethra)
Next to it: Leydig cells –> produce and secrete hormones, LH sensitive
Andrgoens physical actions (fetus + adults)
Main active component: Dihydroxitestosterone (reduction)
Fetus: development of genital organs in men, growth of fetus
Adults: spermatogenesis, anabolism of bone + muscle, development of prim, 2nd. sex characteristics, growth in puberty, sexual behavioral (conversion into oestrogen in brain)
Oestrogens definition + physical actions
Definition:Everything that induces proliferation of endometrium Mainly: 17ß-oestradiol
- triggers LH—> ovulation, breast growth, skin, vaginal secretion, behavioral, osteoblast stimmulation, metabolic actions
Definiton and physical actions Progestrogens
Anything that changes secretory activity of endometrium
Mainly: Progesterone
stimmulates secretion of endometrium and cervix
increases basal body temperature, growth of alveolar in breasts etc.
What are the Main Structure in Ovaries?
Hypothalao-ovarian axis
Changes within menstrual cycle (feedback) + production
Definiton and reason for infertitliy
Definiton: no pregnancy after 12 month of unprotected sex
pituitary failure, prolactinoma (prolactin inhibits LH/FSH), Testicular failure, ovarian failure, polycystic ovarian syndrome
Main phases and hormone levels in menstrual cycle (better overview in notes)
- Early follicular phase (follicles in ovaries develop FSH) follicles slowly produce E2
- Early-mid-follicular phase (one follicle gets bigger than others, production of oestrogen, + feedback loop oestrogen, granulosa cells)
- Mid-follicular phase (low FSH kills smaller follicles, development of Graafian follicle produces E2)
- Late-follicular phase: extremelx high E2, +feedback on LH FSH, high levels of E2 stimmulate ovulation
- Luteral phase (corupus luteum (rest of follicle) produces high amounts of progesterone) preperation for implantation
–> no fertilization:stron neg. feedback –> low levels –> menstruation
Physiological functions of calcium
- Neuromuscular excitability
- Muscle contraction
- Strength in bones
- Intracellular second messenger
- Intracellular co-enzyme
- Hormone/neurotransmitter stimulus-secretion coupling
- Blood coagulation (factor IV)
What are the action of PTH
Parathyroid horomne (synthesized there)
–> up calcium
PTH regulation Feedback
DIHYDROXY-CHOLECALCIFEROL actions
gegenspieler gegen knochenabbau und PO43- ausscheidung
–> preserves bone
Action and regulation of Calcitonin
Synthesized in parafollicular cells of thyroid
Phosphate control
More reabsorbtion:
1,25 (OH)2 D3 in kidney and small intestine
Release by PTH when breaking down bones –> thats why excreted by PTH
Excretion:
Directly PTH + Calcitonin
Fibroblst Growth Factor 23 (FGF 23) –> Kidney excretion (high levels of phosphate and VitD3) –> protection from too much phosphate
Sings and causes for hypocalcaemia
Signs :easy exitable cells : Hand and cheek contraction
- Hypoparathyroidism (ideopathic, low magnesium)
- Pseudo-hypoparathyroidism (resistance to PTH)
- Vit D deficiency (sign: bone matrix too thin (bowing, fractures)
Hypercalcaemia (reasons, differentiation between primary, secondary and tertiary hyperparathyroidism)
Resons:
- Primary hyperparathyroidism –> adenoma (no negative feedback)
(2. Secondary hyperparathyroidism (no hypercalcaemia)–>chronic low Ca2+–> kidney disease (no reabsorbtion possbile, no synthesis of 1,25 (OH)2 D3)) - Tertiary Hyperparathyroidism —> reason for secondary is cured –> but parathyroids went autonomous, dont respod to feedback anymore
- Too much Vitamin D3
What is the effect of Somatotrophin on the body?
How does the V1a receptor of Vasopressin woirk? (intracellular mechanism)
phospholipase C
- PIP2 into inositol triphosphate IP3(and diacyl glycerol, DAG)
- which increase cytoplasmic [Ca2+] and other intracellular mediators (PKC)
- which produce a cellular response
How does the V2 receptor of vasopressin work? (cellular mechanism)
linked via G proteins to adenylcyclase
which acts on ATP to form cyclic AMP
which activates protein kinase A
which in turn activates other intracellular mediators
which produce cellular response (aquaporins, AQP2)
What may be the clinical use of oxytocin?
Induction of Labour at term
- controlled i.v.infusion
Prevention+ treatment of post-partum hemorrhage
- Slow i.v.injection/infusion
- Local pressor action in uterus suppresses bleeding
•FACILITATION OF MILK LET-DOWN
- Intranasal spray
•AUTISM – SOCIAL RESPONSIVENESS??
- Intranasal spray
What is Acromegaly?
What are its symptoms?
It is an excess of growth hormones –> overproduction of Somatrophin
- organs enlarge
- body continues to grow
What is a normal glucose level? (mMol)
4-5mmol
What are the effects of insulin secretion
Decreases Blood glucose
- Increased glycogenesis
- Increased glycolysis
- increased uptake of glucose via GLUT-4 transporters
Increased Protein synthesis and Amino-acid transport
Increased lipogenesis, decreased lipolysis
When is insulin secreted?
Mainly: low blood golucose
But also
- certain AA
- Glucagon
- GI hormones
- PNS
Which effect does somatostatin have on insulin and glucagon secretion?
It inhibits both, insulin and glucagon secretion
What are the effects of Glucagon secretion?
Increased blood glucose
Increased heptic glcogenolysis
Increased gluconeogenesis
- AA transport into liver
- Lypolysis
Which effect does Glucokinase have on insulin secretion?
How?
Glucokinase (Hexokinase IV) transforms Glucose into Glucose-6-phosphate –>
sets off intercellular pathways that trigger insulin release
- ATP generation
- Blockage of ATP-sensitive K+ channel
- allows Ca2+ influx
- Triggers insulin secretion
Which molecule is also referred to the Insulin Glucose sensing molecule?
Glucokinase
Through which receptor does glucose enter a pancreatic ß-cell?
Through the GLUT-2
Compare insulin storage in healthy individuals and individuals with DMT2
In healthy individuals: Stored insulin is present
In DMT2 –> they don’t have stored insulin resulting in steeper increase in blood glucose
What is thyroxine?
T4 (thyroid hormone)
How are thyroid hormones transported in the blood?
- 70-80% thyroid-binding globulin
- albumin (10-15%)
- prealbumin
•Only 0.05% T4 and 0.5% T3 unbound (bioactive components)
What is the main hormone product of the thyroid?
T4 is mainly produced (though T3 is the bioactive form)
Which nerve runs close to the thymus? What does it supply?
the left recurrent laryngeal nerve is close (supplie the vocal cords)
what is the function of the colloid of the thyroid?
It stores thyroglobulin and Thyroxine (also iodinisation + formation of T3/T4 happens here)
What is myxoedema?
It is primary hypothyroidism
How would blood levels for Thyroxine and TSH be in primary hypothyroidism?
It would be a low Thyroxine (can’t be produced) and high TSH (doesn’t receive negative feedback)
How are the effects of untreated hypothyroidism and how is it treated
Patients will die untreated–> high cholesterol leading to stokes and heart attacks
Treatment: Just replacement of T3/4 (monitor until TSH is normal)
Which factor in the adrenals determines, which hormone is produced (e.g. aldosterone and not cortisol)
It is the different content/concentration of the enzymes in different zones (e.g. aldosterone/cortisol only 2 enzymes differ)
low level for reproductive hormone enzymes
How is aldosterone transported in the blood?
- 40% free
- 15% bound to CBG =corticosteroid binding globulin
- 45% Albumin
–> A lot is free
How is Cortisol transported in Blood?
Only 10% free
80% bound to CBG (Corticosteriod binding globulin)
10% Albumin
Why do we have aldosterone, if cortisol can bind to both (MR and GR) receptors?
Some tissues are “protected” from cortisol (e.g. placenta, kidney)
11b-hydroxysteroid dehydrogenase 2 breaks down Cortisol into Cortisone (inactive)
Why get people with primary adrenal failure get tanned?
Becaue of an increased production of ACTH
–> ACTH is a cleaving product of POMC, other product is MSH
MSH (melanocyte stimmulating hormone)
Explain symptoms of primary adrenal failure (Addison’s disease)
no cortisol or aldosterone, so low blood pressure
- Cortisol deficiency
- Salt loss –> no Aldosterone
- Low blood pressure –> No aldosterone
- Eventual death
How do you treat Addison’s disease?
Urgent treatment
- Rehydrate with normal saline
- •Give dextrose to prevent hypoglycaemiawhich could be due to the glucocorticoid deficiency
- •give hydrocortisone or another glucocorticoid
–> Replacement of hormones
What is the difference between Cushing’s syndrome and Cushing’s disease?
Syndrome= can be any cause of too much cortisol
Disease= Pituitary dependant (e.g. pituitary adenoma)
Name four reasons for Cushing’s syndrome
- Taking steroids by mouth (common)
- pituitary-dependent Cushing’s disease (pituitary adenoma)
- Ectopic ACTH (lung cancer)
- adrenal adenoma or carcinoma
How would a patient with Cushing’s syndrome present?
Hypercortisolism
Lemon on stick appearance
- central weight gain
- stretch marks
- proximal myopathy
- moon face
- Diabetes –> long exposure to high glucose
- thin skin, extra hair growth
- hypertension
immunosuppression –> e.g. reactivation of TB?
What are the side effects of (non-medical) use of steroids?
- Hypertension
- Diabetes
- Osteoporosis
- reactivation of infection (immunosuppression)
- easy bruising
- poor wound healing, thin skin
How is the disease with an aldosterone-producing adenoma is called? What are its effects?
It is the Conn’s disease
- hypertension
- oedema
- high Na+, low K+
Explain the structure of a semeniferous tubule
Overall structure:
- Lumen with Spermatozoa
- Cell layer of Sertoli cells (Spermatogenesis, FSH sensitive)
- Zone with Spermatogonia
- Leydig cells associated with it (produce and secrete hormones, LH sensitive)
What is the function of the Seretorli cells?
Which stimmulus do they respond to?
Are located at the cell layer in a seminiferous tubule
- Spermatogenesis
- FSH sensitive
- Produce Inhibin in response to FSH
Explain the location, control and function of the Leydig cells (in male)
Are outside Seminiferous tubule
produce androgens in response to LH (mainly testosterone)
Explain the structure of a Graafian Follicle
From Outside to inside
- Thecal cells (LH sensitive)
- Granulosa cells (FSH)
- Follicular Fluid
- Ovum
In which phase of the ovarian cycle is oestrogen produced?
Which effect does this have on the endometrium?
It is produced in the follicular phase of the ovarian cycle and promotes proliferation of the endometrium
In which phase of the ovarian cycle is oestrogen and progesterone produced?
Which effect does it have on the endometrium?
It is produced in the Luteal phase and causes the secretory phase of the endometrium (preparation for arrival of the Egg)
Explain the Levels of FSH and LH in the menstrual cycle and how they change
Both: about baseline til Follicular phase
What is the first part of the menstrual cycle?
What happens during this phase?
- Early follicular face
FSH dependant development of the follicles in the ovaries
Follicles produce Progesterone and Oestradiol which has a negative feedback on Hypothalamus/Pituitary —> Levels fall
What happens in the early-mid-follicular phase of the menstrual cycle?
Ho do levels of LH, FSH, Oestrodiol and Progesterone change?
The follicle most sensitive to FSH gets bigger –> induced autocrine feedback loop of E2
- (more granulosa cells, produce more E2 (oestrogen), more oestrogen produce more granulosa cells
FSH and LH stay the same or fall slightly (because of feedback)
Progesterone does not change
Oestrogen increases
What is the Graafian Follicle?
What happens to the other follicles?
What does it produce?
The largest follicle no longer requires FSH to develop and proliferate
A fall of FSH kills other follicles that can’t develop FSH independently
It keeps growing and producing large amounts of E2
What happens during the mid-follicular phase?
Graafian follicle develops (produces E2)
other follicles get killed by fall of FSH
–> increase of oestradiol + inhibin
-ve feedback on FSH reduces levels,
No change in levels of LH/Progesterone
What happens during late follicular phase of ovulation?
Extremly high levels of E2 (produced by Graafian Follicle) induce +ve feedback on GnRH and LH
High E2 levels of E2 and LH/GnRH trigger ovulation
What happens during the Luteal phase of the menstrual cycle?
2nd phase of cycle
high levels of progesterone produced by Corpus Luteum
–> prepares for implantation
If no fertilisation: -ve feedback of inhibin, E2 and Progesterone on GnRH/ LH+FSH
What is the bioactive form of Testosterone?
How is testosterone transported in blood and seminiferous fluid
Active form: DHT
–> Dihydrotestosterone
Transport:
- 60% bound to Sex hormone binding globulin (SHBG, blood) or Androgen binding globulin (seminiferous fluid)
- Albumin 38%
- 2% free ( = bioactive)
How is the bioactive form of Oestrogen?
E2= 17ß- Estradiol
What kind of receptors does the Parathyroid hormone bind to?
What is its mechansim of action in the cell?
It binds to a G-protein coupled receptor–>
•Activation of adenyl cyclase, but also probably PLC as second messenger systems
What do osteoblasts/osteoclast do?
What is their function in calcium metabolism?
Osteoblast:
- Built bone (need Ca2+)
- inhibited with Parathyroid hormone
Osteoclasts
- break down bone (release Ca2+)
- inhibited by Calcitonin/ stimulated by Parathyroid hormone
What is the activated form of Vitamin D3? What are its Names?
1,25(OH)2 Vit D3, Calcitriol, dihydroxi-cholecalciferol
WHat is the effect of Fibroblast-Growth factor 23?
It is a factor that influences Phosphate
- is stimmulated by a combination of hight levels of Phospate and VitD3
- Drives Phosphate secretion
- Negative feedback on Calcitriol
Which effect does insulin have on the GLUT-4 receptors?
Where are these receptors most abundant?
Insulin recruits the GLUT-4 receptor vesicles to the membrane when binding to the insulin receptors
They are most abundant in muscle and adipose tissue
Through which receptor is Glucose taken up into muscle and adipose tissue?
Via the GLUT-4 receptor
Which effects does Insulin have on proteins and muscle cells?
- Insulin INHIBITS proteolysis, Cortisol STIMULATES it.
- Insulin INHIBITS oxidation of amino-acids in the cell.
- Insulin STIMULATES re-synthesis of proteins from amino-acids.
- –> This means less amino-acids leave the cell to go to the liver to be used to produce glucose.
Which hormones stimulate gluconeogenesis?
Glucagon
Somatotrophin
Cortisol
Catecholamines
What is Hepatic glucose output? Which two processes normally contribute to this?
it is the amount of synthesized glucose that leaves the liver
There are two mechanisms:
- Gluconeogenesis
- Glycolysis
Which effect does insulin have on the liver?
It stimmulates
- protein synthesis
- glycogen formation
It inhibits
- Gluconeogenesis
- Ketone-body production
- Glycolysis
Which effect does insulin have on adipose tissue?
It stimulates
- Fat entering the cell (via activation of lipoprotein lipase)
- Formation of triglycerides
It inhibits:
- Lipolysis
Which effect does cortisol have on the uptake of glucose into the cell?
It tends to inhibit uptake
In which tissues is insulin resistance found?
What is the part that does not work properly?
Insulin resistance resides in the
- LIVER
- MUSCLE
- ADIPOSE TISSUE
but note that the receptors for insulin are normally functioning, the post-receptor effect is faulty.
Which substances are normally increased or decreased as a result of Type 2 diabetes?
Insulin resistance causes
An increase in
- Non-esterified fatty acids
- Triglyceride
- LDL cholesterol
A decrease in
- HDL
- VLDL clearance (decrease in lipoprotein lipase)
