Endocrinology Quiz Questions

Question 1

Quiz question 1:

The anterior pituitary gland is a major component of the endocrine system and regulates several physiological processes.

What is the embryological origin of the anterior lobe of this gland?

Answer 1

The anterior lobe of the pituitary gland arises from an up-growth of ectodermal cells from the roof of the primitive pharynx.

AND GET FAMILIAR WITH DIAGRAMS

Question 2

Quiz question 2: What effects does this growth factor 1 normally have on cells?

Answer 2

Stimulates:

• Cell growth (hypertrophy)
• Cell number (hyperplasia)
• Increases the rate of protein synthesis
• Increases the rate of lipolysis in adipose

Question 3

Quiz question 3: What is growth hormone also known as?

Answer 3

Somatotropin

Question 4

Quiz question 4: A 51 year old woman with a pituitary macroadenoma attends a routine clinic with her endocrinologist. During the consultation she mentions that she has recently been experiencing blurred vision while watching television, trouble scanning a page when reading and is finding that she frequently bumps into objects when walking around the house.

What is the most likely aetiology of these recent visual complications?

Answer 4

The pituitary is in close proximity to the optic chiasm so growth of the adenoma can compress the optic nerves (this is called a Mass-effect) resulting in visual field defects.

Question 5

Quiz question 5: A surgeon operates on a 56 year old woman to remove a pituitary adenoma. He gains access to the adenoma by inserting an endoscope and his surgical instruments through her nose.

Which surgical procedure was used by this surgeon?

Answer 5

Transsphenoidal surgery

Question 6

Quiz question 6: Name a Dopamine receptor agonist

Answer 6

Bromocriptine

Question 7

Quiz Question 8: CNS regulates GH secretion via inputs into the hypothalamus affecting GHRH and somatostatin levels.

Describe some of these

Answer 7

Increase in GH secretion:

• Deep sleep = surge in GH secretion
• Fasting = ↑ GH secretion
• Decreased glucose/FA = ↑ GH secretion
• Exercise= ↑ GH secretion
• Stress ie trauma, surgery, fever = ↑ GH secretion

Decrease in GH secretion:

• REM sleep = ↓ GH secretion
• Obesity = ↓ GH secretion
• Increase in glucose or free fatty acids = ↓ GH secretion

Question 8

Quiz question 7: An endocrinologist conducts an oral glucose tolerance test on a 49 year old woman as part of her investigations to determine if the woman has acromegaly.

What blood result would be expected from this test if the woman does have acromegaly?

Session 11

Answer 8

GH would not drop:

Acromegaly cannot be diagnosed simply by measuring plasma GH because this varies naturally so much during the day. Typically IGF-1 would be measured which varies less and an oral glucose tolerance test performed. Growth hormone level is linked to plasma glucose. In a normal healthy person without acromegaly, a high blood glucose would inhibit GH production by the anterior pituitary. Thus, in an oral glucose tolerance test you purposely raise blood glucose and deterimne the plasma GH level. The patient drinks 75 g of glucose solution and over 2 hours plasma glucose and GH are monitored. If GH doesn’t drop to below 1 ng/mL (as would be expected in a normal healthy patient) this would confirm acromegaly.

Question 9

Quiz question 8:
A 50 year old woman is diagnosed with an aldosterone secreting adrenal adenoma (Conn’s syndrome).

What would this patient develop as a result of her disease?

Answer 9

Low serum potassium
CORRECT. Mineralocorticoid excess is associated with hypokalaemia. This is because aldosterone, acting on mineralocorticoid receptors within cells of the distal tubules and the collecting duct of the kidney nephron, upregulates and activates the basolateral Na+/K+ ATPase. This pumps three sodium ions out into the interstitial fluid and two potassium ions into the cell from the interstitial fluid. This creates a concentration gradient which results in reabsorption of sodium ions and water (which follows the sodium) into blood and secretion of potassium ions into the lumen of collecting duct which are excreted in urine.

Question 10

Quiz question 9: Angiotensin-converting enzyme (ACE) plays an important role in regulating blood pressure by facilitating the cleavage of angiotensin I into the vasoconstrictor angiotensin II.

In the capillaries of which organ does this conversion mainly occur?

Answer 10

CORRECT. Angiotensin I is converted to angiotensin II by removal of two C-terminal amino acid residues by angiotensin-converting enzyme (ACE) within the lung capillaries

Question 11

Quiz question 10: The peptide angiotensinogen is cleaved at the N-terminus by the protease renin.

Which organ synthesises and releases this peptide into blood?

Answer 11

CORRECT. The liver produces angiotensinogen which is cleaved first by renin in plasma to form angiotensin I and then by angiotensin converting enzyme (ACE) in the lungs to form angiotensin II.

Question 12

Quiz Question 11: Which term is used to describe the excretion of glucose in urine?

Answer 12

CORRECT. Glucosuria (sometimes called glycosuria) is the excretion of glucose in urine. The renal threshold for glucose is ~10 mmol/L. Above this plasma concentration of glucose the kidney is unable to reabsorb glucose and glucose will appear in urine. In pregnancy the renal thrashold for glucose lowers slightly and in old age it increases slightly.

Question 13

Quiz question 12: A 19 year old man eats a beef burger. Shortly after the nutrients from this meal have been absorbed into his bloodstream his pancreas starts to secrete the hormone insulin.

How many disulphide bonds are present in each molecule of this hormone?

Answer 13

3 - There are two disulphide bonds linking the A and B chains of insulin (i.e. inter-subunit disulphide bonds) and one intra subunit disulphide bond within the A chain making a total of 3

Question 14

Quiz question 13:
The diagram below represents a molecule of proinsulin.
What name is given to the yellow segment labelled X?

Answer 14

Correct. C-peptide (“connecting peptide”) connects the A and B chains of proinsulin. C-peptide is cleaved from proinsulin by prohormone convertase 1 and 2 enzymes (acting at the blue amino acids in the diagram above) to yeild the mature insulin hormone. C-peptide is actually co-packaged with insulin in vesicles and is released in equimolar amounts. C-peptide is thought to act as a distinct hormone in its own right with actions distinct from those of insulin. It is important that you are aware of C-peptide and know how it arises since C-peptide is used as a clinical marker for endogenous insulin release (it has a longer half life and so is more stable than insulin in plasma).

Question 15

Quiz question 14: Which member of this family is the primary transporter of glucose in pancreatic β cells?

Answer 15

Correct. GLUT2 is the primary glucose transporter in pancreatic beta cells allowing the glucose entry that ultimately regulates insulin synthesis and release by casuing an increase in ATP concentration. GLUT2 is also the major transporter in liver. It is a bidirectional transporter, allowing glucose to flow in both directions (both out of and into the hepatocyte). GLUT2 therefore allows the hepatocytes to export glucose made by gluconeogenesis into the blood. GLUT2 is not regulated by insulin

Question 16

Quiz question 16: Pancreatic β cells in the islets of Langerhans play a key role in plasma glucose homeostasis.

What effect would an increase in the intracellular concentration of ATP have on hormone secretion by these cells?

Answer 16

Increased insuin secretion. This is how the β cell senses an increase in plasma glucose. More ATP produced from the metabolism of glucose results in inhibition of the ATP-sensitive potassium channels (KATP channels). Less positively charged potassium leaving the cell through KATP channels results in depolarisation of the plasma membrane (i.e. makes the resting membrane potential less negative). This depolarisation is sensed by voltage activated calcium channels which open allowing calcium to flow down its electrochemical gradient into the cell. It is this influx of calcium ions into the β cell that activates the insulin containing vesicles causing them to fuse with the plasma membrane and release insulin.

Question 17

Quiz question 17: The ATP sensitive potassium channel KATP plays a key role in regulating insulin secretion by pancreatic β cells.

What effect would a decrease in the intracellular concentration of ATP have on these channels?

Answer 17

More KATP channels would be in the open state.
ATP-sensitive potassium channels (KATP channels) are inhibited by ATP. A fall in ATP concentration would therefore result in more channels being open. This will cause more positively charged potassium ions leaving the cell through KATP channels resulting in the plasma membrane becoming hyperpolarised (i.e. the resting membrane potential becomes more negative). A more negative membrane potential will make the cell less excitable making it more difficult for voltage activated calcium channels to open. As it is influx of calcium ions into the β cell from the voltage activated calcium channels that drives the fusion of vesicles and subsequent release of insulin, a decrease in intracellular ATP (resulting from a lower concentration of glucose) will prevent insulin release.

Question 18

Quiz question 17: The ATP sensitive potassium channel KATP plays a key role in regulating insulin secretion by pancreatic β cells.

What effect would an increase in the intracellular concentration of ATP have on these channels?

Answer 18

More KATP channels would be in the closed state
Correct. ATP-sensitive potassium channels (KATP channels) are inhibited by ATP. A rise in ATP concentration would therefore result in more channels being closed. This will cause less positively charged potassium ions leaving the cell through KATP channels resulting in the plasma membrane becoming depolarised (i.e. the resting membrane potential becomes less negative). This depolarisation triggers the opening of voltage activated calcium channels. It is this influx of calcium ions into the β cell from the voltage activated calcium channels that triggers the fusion of vesicles and subsequent release of insulin.

Question 19

Quiz question 18: A 41 year old man eats a meal. Shortly afterwards the concentration of the hormone insulin rapidly increases in his blood.

What has occurred in the man’s pancreatic beta cells to initiate this rise in hormone concentration?

Answer 19

Plasma membrane has depolarised Correct. An increase in plasma glucose from a meal would result in more ATP being produced from the metabolism of glucose within the pancreatic beta cells resulting in an inhibition of the ATP-sesnsitve potassium channels (KATP channels). Less positively charged potassium leaving the cell through KATP channels results in depolarisation of the plasma membrane (i.e. makes the resting membrane potential less negative). This depolarisation is sensed by voltage activated calcium channels which open allowing calcium to flow down its electrochemical gradient into the cell. It is this influx of calcium ions into the β cell that activates the insulin containing vesicles causing them to fuse with the plasma membrane and release insulin.

Question 20

Quiz question 19: Shortly afer eating a meal the plasma insulin concentration in a 19 year old male medical student rapidly rises. Vesicles containing this hormone within his pancreatic beta cells have fused with the plasma membrane releasing their contents into his bloodstream by exocytosis.

A rise in the concentration of which intracellular ion has directly caused this fusion?

Answer 20

Ca2+ Correct. A rise in plasma glucose from the meal will result in more glucose being taken up by the pancreatic beta cells. As this glucose is metabolised within the beta cells ATP concentration will rise. ATP-sensitive potassium channels (KATP channels) are inhibited by ATP. A rise in ATP concentration would therefore result in more KATP channels being closed. This will cause less positively charged potassium ions leaving the cell through KATP channels resulting in the plasma membrane becoming depolarised (i.e. the resting membrane potential becomes less negative). This depolarisation triggers the opening of voltage activated calcium channels. It is this influx of calcium ions into the β cell from the voltage activated calcium channels that triggers the fusion of vesicles and subsequent release of insulin.

Question 21

Insulin is a key hormone in metabolism and is produced by pancreatic beta cells in the islets of Langerhans.

Which option depicts the correct sequence for the synthesis of this hormone.

Answer 21

Correct. Well done! Insulin is synthesised as pre-proinsulin (a single-chain polypeptide of 109 amino acids) on ribosomes associated with the rough endoplasmic reticulum. The pre-part (23 amino acids) is a signal peptide that ensures the newly synthesised protein enters the cisternal space of the endoplasmic reticulum. The signal peptide is removed once the molecule enters the endoplasmic reticulum. The remaining proinsulin (86 amino acid, single-chain polypeptide) folds to ensure that there is correct alignment of the cysteine residues and the correct disulphide bonds form. Proinsulin is transported from the endoplasmic reticulum to the trans-Golgi apparatus and packaged into storage vesicles. Proteolysis in the storage vesicles removes a connecting peptide (C-peptide) of 31 amino acids together with four basic amino acids (3 arginine and 1 lysine) from near the middle of the chain. This breaks the single chain into two chains that are held together by disulphide bridges i.e. the mature insulin molecule. The storage vesicles contain the products of proteolysis i.e. insulin and C-peptide in equimolar amounts and a small amount of unchanged proinsulin. The entire contents of the storage granules are released during secretion. As C-peptide is released with insulin in equimolar amounts, its level in plasma is a useful marker of endogenous insulin release. Measurement of plasma C-peptide levels in patients receiving insulin can be used to monitor any endogenous insulin secretion.

Question 22

A 20 year old man presents to his GP with polyuria, polydipsia and recent unexplained weight loss. Subsequent investigations lead to a diagnosis of type 1 diabetes mellitus, a disease caused by the autoimmune destruction of β-cells within the pancreas.

From where does this organ emerge as an outgrowth during embryonic development?

Answer 22

Foregut.
Correct Well done. The pancreas is a large gland of endodermal origin that forms during embryonic development from two buds that arise from the duodenal part of the foregut.

Question 23

A 39 year old mother presents to her GP worried that her 4 month old baby is always thirsty and urinates very frequently. Subsequent investigations reveal that the baby has neonatal diabetes mellitus.

Mutations in the gene coding for which protein could have resulted in this very rare disease?

Answer 23

Kir 6.2
Correct. Well done! This was a distinction level question. Kir6.2 is the pore forming subunit of the ATP-sensitive potassium channels (KATP) expressed in pacreatic β cells. These channels are inhibited by ATP. A fall in ATP concentration would therefore result in more channels being open. This will cause more positively charged potassium ions leaving the cell through KATP channels resulting in the plasma membrane becoming hyperpolarised (i.e. the resting membrane potential becomes more negative). A more negative membrane potential will make the cell less excitable making it more difficult for voltage activated calcium channels to open. As it is influx of calcium ions into the β cell from the voltage activated calcium channels that drives the fusion of vesicles and subsequent release of insulin, a decrease in intracellular ATP (resulting from a lower concentration of glucose) will prevent insulin release.
Mutations in the Kir6.2 gene will therefore disrupt the regulation of insulin release resulting in neonatal diabetes mellitus

Question 24

In 1869 an anatomist made the first careful and detailed description of the microscopic structure of the pancreas. He described several different types of cells which formed numerous “cell heaps” throughout the gland.

Who was this anatomist?

Answer 24

Paul Langerhans

Question 25

A 17 year old girl with type 1 diabetes mellitus self administers a subcutaneous injection of the hormone insulin in order to control her plasma glucose level.

What would be the result of this injection?

Answer 25

Plasma C-peptide concentration would remain the same CORRECT. Connecting peptide (C-peptide) is cleaved from proinsulin during the biosynthesis of insulin and is released in equimolar amounts to insulin from pancreatic β cells. However, commercial insulin preparations for injection just contain insulin (no C-peptide is added to the preparation). For this reason measuring C-peptide can give an indictaion of any residual endogenous insulin secreting capacity of a diabetic receiving insulin injections since any C-peptide must have come from endogenous insulin synthesis rather than injected insulin. Since C-peptide is thought to be a hormone in its own right, many would argue that commercial insulin preparations should also contain this peptide, especially as it has been shown to help alleviate some of the long term microvascular complications associated with diabetes (e.g. nephropathy, retinopathy).

Question 26

A 24 year old man with type 1 diabetes mellitus is taken to the emergency department because of drowsiness, confusion, fever, cough, diffuse abdominal pain, and vomiting. Subsequent investigations lead to a diagnosis of diabetic ketoacidosis.

Which finding would be consistent with this diagnosis?

Answer 26

Arterial ph 6.9

Question 27

A 31 year old woman with type 1 diabetes mellitus is admitted to the emergency department in a confused state with vomiting and fever. She is hyperventilating and keeps asking the nurse for water because she feels so thirsty. The doctor notices a smell of acetone on the patient’s breath and a urine dipstick tests strongly positive for ketone bodies. The doctor makes a diagnosis of diabetic ketoacidosis and commences fluid and electrolyte therapy immediately.

Which feature of the patient’s presentation is a direct result of hyperglycaemia?

Answer 27

Polydipsia

Question 28

A 58 year old man has his fasting plasma glucose concentration measured as part of a routine checkup.

Which value would be considered normal for this parameter?

Answer 28

Correct. 5 μmol/ml equates to 5 mmol/litre. The normal range for plasma glucose is 3.3 to 6.0 mmol/litre. As future clinicians, it is essential that you know the normal plasma concentration for glucose. You would normally be given glucose concentration in mmol/litre so well done if you saw through this “trick question”!

Question 29

A 46 year old woman with type 2 diabetes mellitus is prescribed the drug metformin to help control her plasma glucose.

What is the mode of action of this drug?

Answer 29

Decreases gluconeogenesis. Correct. Metformin inhibits hepatic gluconeogenesis. This would act to lower plasma glucose which is the desired effect in a patient with Type 2 diabetes.

Question 30

A 43 year old man with type 2 diabetes mellitus attends clinic for a routine checkup. As part of his assessment the doctor measures a specific glycated form of haemoglobin in his blood in order to assess the effectiveness of his lifestyle modifications and current drug regime in controlling his plamsa glucose.

Which form of haemoglobin was measured in this patient?

Answer 30

HbA1c is the glycated form of haemoglobin measured to identify the average plasma glucose concentration over prolonged periods

Question 31

A 53 year old woman with type 2 diabetes mellitus attends clinic for a routine checkup. As part of her blood tests the doctor measures her plasma HbA1c

By which process is this type of haemoglobin formed?

Answer 31

Glycation. Correct. Glycation is a non-enzymatic random process that disrupts protein structure and function. If proteins are in contact with a high concentration og glucose for prolonged periods they will become covalently bound to glucose by the process of glycation

Question 32

A 39 year old man with abdominal obseity and a BMI index of 40 kg/m2 is diagnosed with metabolic syndrome.

Which change in blood lipid profile would be consistent with this diagnosis?

Answer 32

Reduced plasma HDL. CORRECT. Reduced HDL (known as “good cholesterol” to the lay person) is one of the diagnostic criteria for metabolic syndrome.

Question 33

A 6 year old girl presents to her GP with polyuria, polydipsia and recent weight loss.

What is the most likely pathology resulting in her condition?

Answer 33

Auto immune beta cell destruction - These are the classic triad of symptoms that present with type 1 diabetes mellitus

Question 34

A 19 year old man with type 1 diabetes mellitus attends the Diabetes clinic for his regular check-up. A blood sample is taken for routine monitoring and from the results the doctor concludes that patient’s pancreas has completely stopped producing any insulin.

Which measurement allowed the doctor to make this conclusion?

Answer 34

Plasma C-peptide level. Correct. Well done! As C-peptide is released with insulin in equimolar amounts, its level in plasma is a useful marker of endogenous insulin release. Measurement of plasma C-peptide levels in patients receiving insulin can therefore be used to monitor any endogenous insulin secretion because medical preparations of insulin to be used as a drug for injection into patients does not contain any C-peptide.

Question 35

A 52 year old man with a BMI of 30.1 kg/m2 is found to have a random plasma glucose of 11.9 mmol/L at a routine NHS health check. A urine dip stick shows glycosuria and absence of ketone bodies. The GP requests a fasting plasma glucose the following morning which gives a value of 9.0 mmol/l. A diagnosis of type 2 diabetes mellitus is made and the GP discusses management strategies with the patient centered around lifestyle modifications. Three months later the GP assesses the man again and finds that he has a BMI of 30.9 kg/m2 and a HbA1c level of 9%.

What would be the next most appropriate step in managing this patient’s condition?

Answer 35

metformin

Question 36

An 11 year old girl is taken to her GP by her mother. She is concerned that her daughter has recently lost weight, always feels thirsty, despite drinking large volumes of water, and frequently needs to pass urine. The GP asks the girl for a urine sample and conducts a urine dipstick test which tests positive for glucose (glycosuria).

What has resulted in this abnormal urine dipstick test result in this patient?

Answer 36

Plasma glucose has exceeded the renal threshold for glucose