Endocrinology Flashcards
What is an endocrine gland?
A group of cells which secrete messenger molecules directly into the bloodstream
What is a hormone
A bioactive messenger molecule secreted by endocrine glands into the blood.
Where is secretin released from and where does it act?
Secretin is released from the Small intestine - duodenal ‘S’ cells and acts in the pancreas
What does Secretin do?
Stimulates bicarbonate-rich secretions in the pancreas in response to acid chyme from the stomach
Define endocrine
A hormone’s action on target cells at a distance
Define paracrine
A hormone’s action on nearby target cells
Define autocrine
A hormone having an effect on its immediate source (same cell)
Define cryptocrine
A hormone having a ‘hidden’ effect within its own cell production
State x3 differences between the endocrine and nervous systems
Endocrine = Release of chemical into bloodstream, effect can be on many target cells around the body, longer effect (can be up to days).
Nervous system = Release of chemical across a synapse, effect is restricted to specific target cells innervated (shorter effect within milliseconds).
For a hormone to have an effect what must a tissue have?
Tissues must express certain receptors.
Name x5 endocrine glands
Pituitary gland, Parathyroid gland, Adrenal gland, Pancreas and gonads.
What is an alternate name for the anterior pituitary gland?
Adenohypophysis
What is an alternate name for the posterior pituitary gland?
Neurohypophysis
What are the three classifications of hormones?
Protein/ polypeptide hormones, steroid hormones and miscellaneous.
All Steroid hormones derive from which compound?
Cholesterol
Name in ascending size order from small peptides - intermediate peptides - complex peptides
TRH < Insulin < LH
Where are proteins synthesised?
In the Rough Endoplasmic reticulum
What is the structure of the hormone before it is active?
Pre-hormone to Pro-hormone which is cut and transported to the GA where it is processed by proteolytic enzymes to form the active hormone.
What is the difference between the Pre-hormone and Pro-hormone?
Pre-hormone = shorter (40 aas) Pro-hormone = longer (240aas)
How is the protein transported from the Golgi Apparatus to the circulation?
Protein is stored in vesicles which fuse with the membrane and are moved out of the cell via exocytosis.
What is the difference between a polypeptide and a protein?
A polypeptide is a single chain whereas a protein is a more complex structure.
What is the difference between how protein and steroid hormones are exported from the cell?
Steroid hormones move freely across the cell membrane whereas protein hormones are packed into secretory granules.
What is the difference between the fatty acid backbone and the steroid backbone?
Fatty acid backbone = glycerol
Steroid backbone = cholesterol
Where is ACTH produced?
The corticotroph cell within the anterior pituitary gland
Briefly describe the process of ACTH synthesis
The amino acid moves from the capillary to the Corticotroph cell cytoplasm where proteins are synthesised on the ribosome. mRNA moves from the Corticotroph nucleus to the cytoplasm on the ribosome and is translated to POMC in the ER. POMC is transported to the GA and processed (cut) by proteolytic enzymes forming ACTH.
Which is the protein hormone pro-hormone?
POMC -
What is an example of a protein hormone?
ACTH
Which blood vessels are pituitary hormones secreted into?
Pituitary capillary
What type of cells are corticotrophs?
Endocrine cells
What type of hormone is Cortisol?
A steroid hormone
Where is cortisol produced?
The adrenal cortex
Name x3 causes of short stature
Hypothyroidism, lack in Growth hormone, malnutrition
How would you test for growth hormone levels?
Insulin induced hypoglycaemia
How would you test for growth hormone levels?
Insulin induced hypoglycaemia.
Take base readings of blood glucose and growth hormone and then give insulin injection.
What would you expect to happen to the osmolarity of urine during a water deprivation test
Increased osmolarity
What is an alternative form of vasopressin that can be given as a nasal spray.
DDAVP (desmopressin)
Concentrated urine has what kind of osmolality?
High osmolality
Compare AVP (arginine vasopressin) with DDAVP
AVP can only be given by injection whereas DDAVP can be given by nasal spray.
DDAVP is selective for the V2 receptor limiting effects to the kidney. No adverse vasoconstrictive effects.
What can DDAVP be used to treat
Diabetes Insipidus
How is Cholesterol carried into cells?
By LDLs and their receptors through endocytosis. LDLs are then stored in fatty acid esters and released via esterases. Free cholesterol then moves to the mitochondria via the StAR protein.
What are LDLs stored as within the cell?
Fatty acid esters
How is free cholesterol moved into the mitochondria?
Via the StAR protein (Steroidogenic acute regulatory protein).
Which is the rate limiting step in steroid synthesis of cholesterol?
Moving free cholesterol from the fatty acid ester to the mitochondria via the StAR protein. This is the RLS as cholesterol cannot be made if it is not transported to the mitochondria.
What makes steroids soluble?
Their cholesterol backbone
Once cortisol is made from cholesterol, how does it get back into the circulation?
Through freely diffusing back to the blood.
Is the pituitary gland part of the brain?
No. It is peripheral tissue which sits below the hypothalamus.
In which organelle is POMC made from mRNA?
The RER
Which organelle packs POMC into vesicles?
The Golgi Apparatus
Which are more soluble - protein or steroid hormones? How does this affect how they are carried within the circulation?
Protein hormones are soluble meaning they circulate freely in the blood stream. Steroids are insoluble and so are bound to plasma proteins.
Which plasma protein has low specificity and can bind to many steroid hormones?
Albumin
Name x3 specific plasma proteins and what they bind to to carry round in the circulation
CBG - Cortisol binding
TBG - Thyroid binding
SHBG - Testosterone/ oestradiol binding
When may CBG and cortisol levels be important to be measured?
During pregnancy
Does albumin bind strongly or weakly to proteins?
Weakly; non specific.
How is Cortisol bound to CBG?
With high affinity. Majority of cortisol’s structure is bound to the CBG - remaining to tissues.
If a steroid hormone is heavily plasma protein bound, can it still access
tissues?
Yes, as there is still a component of its structure e.g. cortisol, which is bound to tissues
What are the three things that affect how a hormone is released from its target cell?
- Number of receptors on target cell
- Hormone concentration in circulation
- Affinity of hormone by receptor
How does ACTH affect cholesterol release
ACTH binds to GPCR on the adrenal cortex causing dissociation of alpha subunit from Gs protein = activates adenylate cyclase and converts ATP to cAMP. Activates PKA which increases activation of StAR and esterases.
ACTH causes esterase and StAR protein activation = increase cholesterol release to the mitochondria.
Describe the mechanism of cortisol work in cell signalling?
Cortisol freely diffuses into the cell cytoplasm and binds to glucocorticoid receptors in the cytoplasm. This complex then binds to DNA binding sites and alters DNA transcription and protein synthesis, upregulating and downregulating protein production.
Does Cortisol bind to any receptors to get from the circulation into the cell?
No. It passively diffuses.
Which target would cortisol bind to induce negative feedback within the
anterior pituitary?
Glucocorticoid receptor; cortisol is functioning meaning anterior pituitary gland is not required to make any more cortisol.
What is another name for the pituitary gland?
Hypophysis
What is another name for the anterior pituitary gland?
Adenohypophysis
What is another name for the posterior pituitary gland?
Neurohypophysis
What does fenestrated mean?
Leaky e.g. primary capillary plexus in the anterior pituitary gland = allows communication between the hypothalamic nuclei and the pituitary gland.
Describe the portal circulation in the anterior pituitary gland
Superior hypophysial artery feeds into the primary capillary plexus within the median eminence of the anterior pituitary gland. The primary capillary plexus drains into the secondary capillary plexus and then through to the venous system via the cavernous sinus.
What is a portal network?
Where blood drains from the systemic circulation drains from one capillary network to another before returning to the heart.
Where do short hypothalamic neurones project to in the pituitary gland?
The median eminence
Where do long hypothalamic neurones project to in the pituitary gland?
The neurohypophysis (Posterior pituitary gland).
How do neurosecretions from the hypothalamus get into the pituitary gland?
Through the primary capillary plexus.
What are the three types of adenohypophysial hormones?
Proteins, Glycoproteins and Polypeptides.
What are examples of glycoprotein hormones and what differentiates between them?
LH, FSH and TSH. All made up of alpha and beta subunits. Beta subunits are what differ between them.
How are hormones secreted from the hypothalamus?
In a pulsatile fashion
Which hormone stimulates Growth hormone release and which inhibits release?
Growth hormone is stimulated by GHRH - Growth hormone releasing hormone and inhibited by somatostatin.
What is another name for the growth hormone?
Somatotrophin
Which hormone stimulates Prolactin release?
Thyrotrophin releasing hormone - only has minute effects. Must inhibit dopamine for majority of Prolactin stimulation.
Which hormone inhibits Prolactin release?
Dopamine
On which organ are many growth hormone receptors found?
Hepatocytes = causes production of IGFs which stimulate growth.
Name x3 effects of growth hormone
Increased protein synthesis, gluconeogenesis and lipolysis.
Name x3 stimulants of growth
Sleep, oestrogens, stress and exercise.
What does T4 stand for and what is another name for it?
Triiodothyronine. Thyroxine.
What is characterised by hypothyroidism?
High TSH; low T3, T4
What effect does oestrogen have on TRH?
Promotes TRH production
Name two hormones which inhibit TRH release from the hypothalamus
Glucocorticoids and somatostatin
Where is TSH released from?
The anterior pituitary gland
How is the majority of T3 made?
From deiodination of T4.
Which hormones increase blood glucose?
Glucagon, catecholamines, cortisol, somatotrophin
Which is the most common form of Diabetes?
T2DM
What are the islets of langerhans made up of?
Alpha, beta and delta cells.
What do delta cells of the islet of langerhans produce?
Somatostatin
Name x3 ways insulin reduces blood glucose
Increases glycogenesis
Increases glycolysis
Increases glucose uptake back into cells
Does insulin increase or decrease fat production
Insulin increases lipogenesis
Does insulin increase or decrease protein synthesis?
Insulin increases protein synthesis
Name the main mechanism of glucagon in increasing blood glucose concentration
Increases hepatic glycogenolysis.
Through which Glut transporter is glucose brought into cells?
Glut 2
What is insulin’s structure made up of?
Alpha and a beta chain linked by disulphide bonds. Beta subunits are membrane bound with tyrosine kinase domains.
What is GLP-1?
Glucagon like peptide = stimulates insulin, inhibits glucose. Secreted in response to nutrients within the gut and increases satiety.
Is vasopressin produced in the posterior pituitary gland?
No; it is produced in the hypothalamus and released from the posterior pituitary gland.
Vasopressin-stimulated water reabsorption involves the insertion of aquaporin-2 molecules into the basal (serosal) membranes of its target renal cells. True or false.
False; they are inserted into the apical membranes of renal cells
Oxytocin is a peptide made up of how many amino acids?
- It is a nonapeptide.
Vasopressin stimulates water reabsorption in the renal proximal tubules. True or false.
False;
Vasopressin V1 receptors are linked to the adenyl cyclase-cyclic AMP system. True or false.
False; this involvement is with V2 receptors.
Upward growth from the buccal cavity forms which lobe of the pituitary gland?
The anterior pituitary gland
Steroid hormones are stored in secretory granules. True or false?
False
All anterior pituitary hormones are polypeptides or proteins/glycoproteins. True or false?
True.
ADH stimulates the release of corticotrophin (ACTH) from the anterior pituitary. True or false?
True.
Where is leptin produced?
Adipocytes
Somatostatin inhibits insulin release. True or false?
True.
What is the approximate weight of the thyroid gland?
25g.
What causes Grave’s disease?
Graves’ disease is caused by anti-TSH receptor antibodies
Is hyperthyroidism associated with weight gain or weight loss?
Weight loss; increased metabolism. BUT will increase appetite.
Which is the ‘post-prandial’ hormone?
Insulin
Name two processes other than gluconeogenesis and glycogenolysis in which we can make glucose?
Lipolysis and Proteolysis
Which enzymes are triglycerides broken down by?
Lipoprotein lipase
Can fatty acids be used to make glucose?
No - only the glycerol component from fatty acids can be used.
Why can the brain not use fatty acids as an energy source?
The brain is made of fat so enzymes cannot be used to break down fatty acids as an energy source.
During prolonged fasting, what does the brain use as an energy source?
Ketones
Does Insulin promote lipolysis or lipogenesis?
Lipogenesis
In which pathway, does Insulin resistance reside?
The PI3/Akt Pathway which has metabolic actions
What is the name of the gland which controls calcium metabolism?
The Parathyroid Gland
What is the adult thyroid gland weight?
20g
What is the origin of the thyroid?
The back of the tongue.
Thyroxine deficiency is associated with what?
Dysfunction in brain development
Define the term ‘Cretin’?
An individual with no thyroid gland who has dysfunction in brain development.
What is the Guthrie Test used to test for?
Phenylketonuria
How would you measure thyroid function?
Measure TSH via the Heel prick test
Where are thyroglobulin and thyroxine found?
Within the colloid of the follicular cell in the thyroid gland
In which gender is thyroid disease more common?
Females
What is myxoedema another word for?
Primary hypothyroidism
When will TSH levels be high?
When there is a lack of T3/T4 production i.e. hypothyroidism
What is the primary cause of hyperthyroidism?
Graves’ Disease. Autoimmune.
What is the mechanism of Grave’s disease?
Antibodies bind and stimulate the TSH receptor.
What is the functional unit of the thyroid gland?
The follicular cell
What is the iodine form in the blood?
I-
What type of enzyme converts iodide to iodine?
Peroxidase
The adrenal cortex is the site of synthesis of catecholamines. True or false.
False. Catecholamines are synthesised in the medulla.
Where is aldosterone synthesised?
In the zona glomerulosa cells
When is aldosterone secreted?
When there is low blood pressure, aldosterone increases sodium reabsorption to increase blood pressure
Cortisol stimulates protein catabolism. True or false?
True
Addison’s disease can be caused by tuberculosis. True or false?
True
Hypoglycaemic episodes are common in patients with Cushing’s syndrome. True or false?
False; high cortisol = high glucose.
Hypoglycaemic episodes are common in patients with Cushing’s syndrome. True or false?
False; high cortisol = high glucose. Type 2 Diabetes is often seen in Cushing’s syndrome
Cushing’s syndrome can be caused by the excessive use of iodine containing compounds. True or false?
False; It may be associated with hyperthyroidism but not caused by it.
What is Addison’s disease?
Low cortisol characterised by primary adrenal failure.
Name x3 Signs/ symptoms you would see in Addison’s disease and why?
Pigmentation of skin; High MSH, hypotension; low cortisol, low aldosterone. Dizziness + fatigue; low cortisol = low glucose, hypoglycaemia.
What is Cushing’s disease?
High levels of cortisol. ‘Disease’ means the cause is a pituitary adenoma.
What is Cushing’s syndrome?
High levels of cortisol characterised generally with weight gain, bruising, proximal myopathy and mood changes. No clear cause
What is polydipsia?
Increased thirst
Which disease is associated with proximal myopathy?
Cushing’s disease.
One patient complains that the shape of her face has changed and that she has gained a lot of weight ‘around her tummy’. She also mentions that she bruises easily, and that a would on her left shin that she had six months ago has not healed. What is the diagnosis?
Cushing’s disease; bruise easily, thin skin, weight gain.
Angiotensin I is a potent vasoconstrictor molecule. True or false?
False.
Testosterone breaks down to form which 2 compounds?
Dihydrotestosterone and 17B-Oestradiol.
Which enzyme breaks down testosterone to oestrogen?
Aromatase
Which enzyme breaks down testosterone to dihydrotestosterone?
5a-Reductase
Give x3 functions of androgens in the fetus?
- Development of male internal and external genitalia.
- General growth
- Behavioural effects
Give x3 functions of androgens in the adult?
- Spermatogenesis
- Protein anabolism
- Secondary sex characteristics
- Pubertal growth spurt
What are oestrogens?
Any substance which induces mitosis in the endometrium.
Give x5 functions of oestrogens
- Induces LH surge at ovulation
- Maturation of the follicle during the menstrual cycle
- Stimulates proliferation of the endometrium
- Increases renal salt and water reabsorption
- Stimulates osteoblasts
- Behavioural influences
Which hormone has protective effects on the cardiovascular system and against osteoporosis?
Oestrogen
What are progestogens?
Any substance which induces secretory changes in the endometrium.
What is the difference between micro and macro prolactinoma?
Micro-lactinoma = <1cm Macro-lactinoma = >1cm
Where is calcium mainly found?
Within the bone as hydroxyapatite crystals
Which form of calcium is active?
The unbound form
Which hormone increases blood calcium?
Parathyroid hormone
Which hormone decreases blood calcium?
Calcitonin
What is Calcitriol also known as?
1, 25 dihydroxycholecalciferol
Where is Calcitonin released from?
The parafollicular cells in the thyroid gland.
Parathyroid hormone binds to what kind of receptor?
GPCR
What affect does Parathyroid hormone have on the kidneys?
Increases PO4 excretion
Increases Ca2+ reabsorption
Stimulates 1a-hydroxylase activity
What are Vitamin D3’s affects on the small intestine?
Increases calcium and phosphate reabsorption.
What is the Parathyroid hormone’s affects on the bone?
Increases osteoclast activity and decreases osteoblasts.
Does the PTH increase or decrease osteoclast activity?
Increases osteoclastic activity to release calcium.
Does Vitamin D3 increase or decrease osteoblast activity?
Increases osteoblastic activity
What is pseudohypoparathyroidism?
PTH resistance - There are sufficient PTH levels but the tissues are resistant to it.
Where does the left adrenal vein drain?
The renal vein
Where does the right adrenal vein drain?
The inferior vena cava
How many veins does each adrenal gland have?
Each adrenal gland has only one vein (but many arteries).
Where is cortisol produced?
Zona Fasiculata and the Zona Reticularis
Where are adrenaline and other catecholamines produced?
Adrenal Medulla
What makes up the adrenal cortex?
The Zona fasciculata, zona glomerulosa and the zona reticularis
What is the function of the parathyroid gland?
To control calcium metabolism
What does an absence of thyroxine do to the basal metabolic rate?
Absence of thyroxine causes a decrease in BMR.
What is the daily treatment intake of thyroxine?
100mg a day
What does TRH stand for?
Thyrotropin releasing hormone
What does TSH stand for?
Thyroid stimulating hormone
What is pretibial myxoedema and when is it seen?
Antibodies stimulate growth of the shin in hyperthyroidism.
Is goitre seen in hypothyroidism or hyperthyroidism?
Both.
How do most hyperthyroidism treatments work?
Target the peroxidase enzyme
What is the name for half-blindness on both temporal lobes?
Bi-temporal hemianopia
What affect does prolactin have on LH and FSH?
Prolactin suppresses LH, FSH.
How can high levels of stress cause someone to miss their menstrual cycle?
Stress is an inducer of prolactin release as it inhibits dopamine. Prolactin suppresses LH and FSH levels.
Define galactorrhoea
Excessive or inappropriate production of milk.
How can a pituitary tumour cause bitemporal hemianopia?
The pituitary tumour impinges upon the optic chiasm disrupting the nerve pathways from the nasal parts of the retina = loss of peripheral vision.
Which is the outermost layer of the adrenal cortex?
Zona Glomerulosa
Which is the innermost layer of the adrenal cortex?
Zona Reticularis
Mineralocorticoids and glucocorticoids are examples of which sub class?
Corticosteroids - produced by the adrenal cortex.
How many carbons does cholesterol have?
27
What is Cholesterol immediately converted to before undergoing further steps to be made into cortisol?
Pregnenolone
The P450c17 enzyme is involved in which synthesis type?
Cortisol synthesis
Which enzyme converts testosterone to oestradiol?
Aromatase
What type of compound is adrenaline?
Amine
Which hormones are high in Addison’s disease?
ACTH and MSH
ACTH derives from which compound?
POMC - Pro-opiomelanocortin
Cortisol can bind to which receptors in comparison with aldosterone?
Cortisol can bind to glucocorticoid and mineralocorticoid receptors, whereas aldosterone can only bind to mineralocorticoids receptors.
Which enzyme converts cortisol to cortisone?
11b-hydroxysteroid dehydrogenase 2 enzyme
What percentage of cortisol is plasma protein bound?
80%
What percentage of aldosterone is plasma protein bound?
60%
Where is there a high concentration of 11B-hydroxysteroid dehydrogenase 2?
The kidney; a lot of active cortisol is converted to cortisone.
Where is renin produced?
In the granular cells of the kidney
Which cells detect varying levels of sodium?
The macula densa cells
How is angiotensinogen converted to angiotensin II?
Angiotensinogen is converted to angiotensin I by Renin and then to angiotensin II by ACE
Where is ACE released from?
The lungs
What is Angiotensin II’s affect on aldosterone?
Increases its production
What is angiotensin II’s affect on K+ and Na+?
Angiotensin II increases aldosterone production which increases tubular Na+ reabsorption in the kidney. Aldosterone increases K+ excretion.
Which hormones control cortisol production?
CRH (hypothalamus) and ACTH (anterior pituitary gland).
What does CRH stand for?
Corticotrophin releasing hormone
Where is the majority of water reabsorbed under aldosterone control?
In the collecting duct
Where is the Na+/K+ pump in the kidney?
In the distal tubule of the kidney
Describe aldosterone’s mechanism of action within the kidney?
Aldosterone binds to mineralocorticoid receptors and stimulates Na+ reabsorption into the distal tubule cell of the kidney. Aldosterone drives Na+ out of the collecting duct through Na+ CHANNELS and Na+/K+ ATPase pump.
Compare how cortisol binds to cortisol compared with mineralcorticoid receptors?
Cortisol binds fully to mineralocorticoid receptors whereas it partially binds to glucocorticoid receptors.
How are aquaporins inserted into the distal tubule membrane?
When ADH binds to the V2 receptor, Aquaporins 2,3 and 4 are inserted into the membrane which allow H20 to flow through.
What actions does cortisol have on glucose?
Cortisol increases glucose levels and so increases glycogenolysis, gluconeogenesis and decreases GLUT 4 transport (to keep glucose in blood).
What affect do glucocorticoids - cortisol, have on free fatty acids?
Cortisol decreases free fatty acids.
How does cortisol increase memory function?
Cortisol upregulates serotonin 5HT receptors.
What affect does cortisol have on inflammation?
Cortisol has anti-inflammatory AND immunosuppressive effects.
Anti-inflammatory: decreases leukocyte, monocyte function and complement activation.
Immunosuppressive: decreases complement and lymphocyte function.
Where are memories stored?
In the Dantate Gyrus
What effect would supraphysiological levels of cortisol have on blood pressure?
Cortisol would be converted to cortisone by 11b-hydroxysteroid dehydrogenase 2 enzyme. This would increase aldosterone needed ……………..
Where are androgens produced in the kidney?
Zona Reticularis e.g. DHEA
Which are the MAIN steroid hormones in males and females?
Males = androgens Females = oestrogen and progesterone
What is the difference in spermatogonia and oogonia number between males and females?
Spermatogonia remain relatively constant through life whereas oogonia are at their maximum at 24 weeks of gestation and after birth decrease.
How many oogonia are present at birth?
2million; There is rapid atresia of oogonia before birth from the 4-6 million
When are oogonia reduced to 0?
Menopause
Describe spermatogenesis
Germ cell > spermatogonia > primary spermatocyte > secondary spermatocyte > spermatid > spermatozoa.
Describe oogenesis
Germ cell > Oogonia > Primary oocyte > secondary oocyte > obum
Describe oogenesis
Germ cell > Oogonia > Primary oocyte where 1st meiosis is halted until puberty > secondary oocyte > ovum.
When do meiosis and mitosis occur in spermatogenesis/ oogenesis?
Spermatogonia > primary spermatocyte = mitosis
Primary spermatocyte > secondary spermatocyte = 1st meiosis
Secondary spermatocyte > spermatid = 2nd meiosis
Oogonia > primary oocyte = mitosis
Primary oocyte > secondary oocyte = 1st meiosis
Secondary oocyte > ovum = 2nd meiosis
When does gametogenesis begin in males compared with females?
At puberty in males.
Which stage of meiosis is halted during oogenesis from the primary oocyte to the secondary oocyte?
Prophase
Where does spermatogenesis take place?
Within the coiled seminiferous tubules
Which structure is between the rete testis and epididymis in the testes?
The vasa efferentia
How do spermatozoa move from the epididymis to the urethra?
Through the Vas Deferens via smooth muscle contraction
Where do spermatozoa mature?
Within the epididymis
Describe the structure of the coiled seminiferous tubule
Lumen surrounded by sertoli cells connected by tight junctions.
Where is the site of testosterone production?
The Leydig cell
Where are FSH and LH receptors produced?
FSH receptors produced in the Sertoli cell
LH receptors produced in the Leydig cell
Which cells produce Inhibin in response to FSH?
Sertoli cells
Describe the structure of the ovaries
Ovarian stroma made up of: the Graafian follicle, follicles and remnants of the corpus luteum.
What is the Graffian follicle?
An ovum, granulosa cells and thecal cells
What molecule do oestrogens and progesterones derive?
Cholesterol
Which are the two phases of the menstrual cycle?
The proliferative and secretory phase.
Oestrogen is seen predominantly in which phase of the menstrual cycle?
The proliferative phase
Progesterone is seen predominantly in which phase of the menstrual cycle?
The secretory phase
Is the basal body temperature higher in the first or second part of the menstrual cycle?
The second half.
Describe the Ovarian cycle
Pre-antral follicle to early antral follicle to late antral follicle to Graafian follicle to ovulation.
Which cells produce androgens in the ovaries?
Thecal cells.
Which cells in the ovaries contain aromatase?
Granulosa cells.
What is the function of aromatase?
Converts androgens to 17B-Oestradiol after ovulation.
Testosterone and aldosterone derive from which common compound apart from cholesterol?
Progesterone
Testosterone is converted to which 2 compounds within the gonads?
Dihydrotestosterone and 17B-Oestradiol.
Which enzyme is required to make 17B-Oestradiol from testosterone?
Aromatase
Which enzyme is required to make Dihydrotestosterone from Testosterone?
5a-Reductase
What is the difference between testosterone and dihydrotestosterone?
DHT is more potent.
Testosterone is converted to which compound in the testes?
TRICK! Depends where in the testes;
Seminiferous tubules=DHT
Sertoli cells =17B-Oestradiol
What is seminiferous fluid?
Semen
Do androgens contribute to protein and bone anabolism or catabolism?
Anabolism. (growth)
Define oestrogen
Any substance which induces mitosis (thickening) in the endometrium (womb).
Which is the main oestrogen in pregnancy?
Oestriol
What is a progesterone?
Any substance which induces secretory changes within the endometrium.
What is the difference between oestrogen and progesterone effects on Na+ reabsorption.
Oestrogen increases Na+ reabsorption. Progesterone decreases Na+ reabsorption; competitive inhibition with aldosterone.
Which hormone stimulates the Sertoli cell to make testosterone?
LH
Testosterone to oestrogen production is what type of reaction?
Aromatisation.
How many months of unprotected sex must a couple be having without pregnancy to be deemed infertile?
12 months
Give x3 diseases which may cause infertility
Pituitary failure
Ovarian failure
Testicular failure
Prolactinoma
What is the term for infrequent periods?
Oligomenorrhoea
How does the graafian follicle form?
It competes with the other follicles by making more oestrogen and gets bigger. There is a positive feedback loop within itself (autocrine). Oestrogen made by follicle stimulates granulosa cells to grow which stimulates further oestrogen production.
What is the LH surge on day 14 caused by?
The positive feedback and release of extremely high levels of oestrogen. Positive feedback to GnRH and LH.
Which hormone does the corpus luteum make?
Progesterone
Which hormones increase and decrease blood calcium levels?
Increased by parathyroid hormone and 1, 25- dihyroxycholecalciferol, decrease by calcitonin.
How many Parathyroid glands are there?
4
PTH binds to receptors on which cell?
The osteoblast which activates RANKL on osteoclasts.
What is FGF23’s effect on phosphate?
FGF23 increases phosphaturia = decreases phosphate reabsorption.
What are Trousseau’s sign and Chvostek’s sign and when are they seen?
Trousseau’s sign: Tetany in the hands
Chvostek’s sign: facial nerve can be tapped to induce a twitch.
Seen in hypocalcaemia
Adenoma can cause what endocrine disorder?
Primary hyperparathyroidism; low calcium means more PTH must be produced but there is no negative feedback.
What affect will hyperparathyroidism have on the bone, kidney and small intestine
Bone fractures
Kidney: Increase PO43- excretion, increase Ca2+ reabsorption, kidney stones
Small intestine: Increase Ca2+ and PO43- absorption = gastric and duodenal ulcers,
What is a hormone?
A bioactive messenger
Name x2 Protein hormones and x2 Steroid hormones
Protein hormones = ACTH, Insulin, LH TRH
Steroid hormones = Cortisol, Vitamin D.
Where are chromaffin cells found?
Within the medulla of the adrenal gland.
Where are cortisol, adrenaline, aldosterone and androgens produced?
The adrenal gland
Aldosterone is what type of substance?
Mineralocorticoid
Describe the relationship between Serotonin and Cortisol
Serotonin increases hippocampus sensitivity to Cortisol.
Cortisol upregulates serotonin 5HT 1A receptor density.
