meh endocrine bb quiz and sm

Question 1

What is the function of α-MSH?

Answer 1

The function of α-MSH is to act on melanocortin-4 receptors to induce appetite.

Question 2

What is the main cause of Cushing’s syndrome? (1 mark)

A benign pituitary adenoma secreting Adrenocorticotropic hormone (ACTH) (Cushing’s disease)

An adrenal tumour secreting excess cortisol (Adrenal Cushing’s)

Being prescribed glucocorticoids

Non-pituitary adrenal tumours producing Adrenocorticotropic hormone (ACTH) and/or Corticotropin-releasing hormone (CRH) (e.g. small cell lung cancer)

Answer 2

Being prescribed glucocorticoids

Question 3

Which of the following is a sign of hyperaldosteronism?

Answer 3

Common signs and symptoms of hyperaldosteronism include high blood pressure, left ventricular hypertrophy, hypernatraemia, and the correct answer here, which is hypokalaemia.

Question 4

Affects of cortisol

Answer 4

Affects of cortisol include catabolism (like increased proteolysis), resistance to stress, anti-inflammatory effects, and depression of the immune system.

Question 5

Which of the following is aldosterone most abundantly bound to?

Answer 5

serum albumin

Question 6

Which of the following correctly describes the route of hormones from the hypothalamus to the pituitary?

Answer 6

‘Hypothalamus – axons – median eminence – hypophyseal portal system – endocrine cells in the anterior pituitary’

Question 7

What is the most common cause of gigantism?

Answer 7

pituitary adenoma

Question 8

Which of the following is the most common cause of hyperprolactinaemia?

Answer 8

prolactinoma

Question 9

symptoms of pituitary adenoma

Answer 9

headaches nausea visual problems

Question 10

Which two substances are produced via the iodination of the tyrosine side chains of thyroglobulin, catalysed by thyroid peroxidase?

Answer 10

Monoiodotyrosine and Diiodotyrosine

Question 11

Which substance is produced by follicular cells in the thyroid gland?

Answer 11

thyrogobulin

Question 12

Through which channels does glucose diffuse into target tissues?

Answer 12

GLUT4

Question 13

Which amino acid of haemoglobin does glucose react with in order to glycate it?

Answer 13

Valine

Question 14

When a patient is diagnosed with type 2 diabetes, approximately what percentage of their β-cells are functioning?

Answer 14

50%

Question 15

3 classic symptoms of diabetes mellitus

Answer 15

excessive thirst, polyuria and weight loss.

Question 16

Which of the following is NOT a characteristic of a dyslipidaemic profile?

Answer 16

Decreased VLDL is the correct answer here because it is NOT a characteristic of the dyslipidaemic profile commonly assocaited with diabetes mellitus.

Question 17

A 45 year old woman presents to her GP with symptoms of excessive urination and excessive thirst. She says she has also visited the pharmacy three times in the past six months for over the counter treatment for genital thrush. Based on these symptoms, which type of Diabetes Mellitus seems a more appropriate diagnosis?

Answer 17

Type 2 diabetes is more likely in this patient as the symptoms have recently come on at age 45. The symptoms of excessive urination and excessive thirst are classical of diabetes. The genital thrush is caused by the presence of glucose in the urine, which encourages the growth of organisms in the genital area.

Question 18

Which of these hormones acts to raise serum calcium levels when there is a PROLONGED reduction in serum calcium?

Answer 18

calcitriol

Question 19

calcitonin

Answer 19

Calcitonin acts to lower serum calcium levels,

Question 20

what raises serum calcium levels

Answer 20

Calcitriol, PTHrP and PTH all are correct here as they act to raise serum calcium levels.

Question 21

Which cells of the parathyroid gland produce PTH?

Answer 21

chief cells

Question 22

Name the peptide precursor of the neurotransmitters αMSH, β-endorphin and ACTH (adrenocorticotropic hormone).

Answer 22

POMC

Question 23

A 45 year old woman with Graves’ disease is experiencing irritability, muscle weakness, sleep problems, tachycardia and poor tolerance to heat. All her symptoms are due to the excess production of the thyroid hormones T3 & T4

Which class do these hormones fall under?

Answer 23

Amine hormones
Correct. The thryoid hormones triiodothyronine (T3) and thyroxine (T4) are amine hormones synthesised from the amino acid tyrosine.

Question 24

The hormones aldosterone, testosterone and progesterone are all synthesised in the body from the same precursor molecule.

What is this precursor molecule?

Answer 24

Cholesterol

Question 25

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 25

plasma membrane has depolarised

Question 26

The insulin receptor mediates the effects of the hormone insulin.

To which class (type) does this receptor belong?

Answer 26

tyrosine kinase

Question 27

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 27

Question 28

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 28

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 29

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 29

Arterial pH 6.9

Question 30

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 30

Metformin
Correct. Well done! Metformin is a biguanide used as an oral hypoglycaemic therapy. It reduces hepatic glucose output by inhibiting gluconeogenesis and as a result, reduces the level of glucose in the blood. Biguanides also tend to make the cells of the body more willing to absorb glucose already present in the bloodstream, and there again reducing the level of glucose in the plasma.

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 45 year old woman with abdominal obseity and a BMI index of 39 kg/m2 is diagnosed with metabolic syndrome.

What are the two most significant factors underlying the aetiology of this syndrome?

Answer 32

insulin resistance and central obesity

Question 33

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.

Why must this hormone be delivered by injection rather than being taken orally in pill form?

Answer 33

Insulin is a peptide hormone so would be broken down in the gastrointestinal tract to its consituent amino acids (rendering it inactive) if it were to be taken orally.

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

Question 35

embryology of AP

Answer 35

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

Question 36

IGF actions

Answer 36

Question 37

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?

Answer 37

GH would not drop. 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.

Question 38

A 57 year old woman with a history of high blood pressure that cannot be controlled with medication is diagnosed with secondary hyperaldosteronism resulting from renal artery stenosis.

Which sign would be present in this patient as a result of her condition?

Answer 38

Low aldosterone : renin ratio
CORRECT. This is the best way to distinguish between a primary (where the ratio would be high) and a secondary aldosteronism.

Question 39

why purple striae in Cushing’s

Answer 39

The central obesity from the cortisol induced redistribution of fat in Cushing’s syndrome stretches the skin. Since the skin is thin and weakened due to the actions of cortisol also increasing proteolysis, “stetch marks” or purple striae can form.

Question 40

A 26 year old woman turns very pale after a dog tries to attack her in the street. As part of the “fight or flight” response the hormone adrenaline was released into her circulation from the adrenal medulla. One of the actions of this hormone is to activate α1-adrenergic receptors present on the vascular smooth muscle cells of cutaneous arteries. Activation of these receptors by adrenaline has induced smooth contraction and vasoconstriction resulting in a decreased blood flow to her skin and therefore her pale appearance.

Which change in second messenger concentration would result from the activation of these receptors?

Answer 40

increased IP3

Question 41

consequence of beta vs alpha receptors

Answer 41

Question 42

Answer 42

A = cushing’s syndrome ( due to the use of glucocorticoid medication)
B = adrenal cushing’s (adrenal adenoma secreting the hormone cortisol)
C = cushing’s disease (pituitary adenoma secreting ACTH)
D = normal
E = ectopic ACTH syndrome

Question 43

cushing’s syndrome blood results

Answer 43

everything low

from medication

Question 44

adrenal cushings blood results

Answer 44

cortisol high
ACTH low

cortisol being secreted from adrenal adenoma

Question 45

cushing’s disease blood results

Answer 45

Cortisol and ACTH high apart from low on high dose dex sup test

pituitary adenoma secreting ACTH

Question 46

adrenal cushing’s vs cushing’s disease

Answer 46

adrenal = cortisol secreted
disease = ACTH secreted

Question 47

A 28 year old woman with abdominal obesity, thin arms and legs, a “moon face”, a “buffalo hump” and purple striae on her stomach is referred to the endocrine unit by her GP. Subsequent investigations show that she has an elevated ACTH and a high cortisol, neither of which are suppressed by high dose dexamethasone.

What condition is this patient most likely suffering from?

Answer 47

ectopic ACTH syndrome

Question 48

A 53 year old woman presents to her GP feeling quite unwell. A blood test and 24 hour urine analysis show elevated levels of catecholamines and catecholamine products. The GP refers the woman to the endocrine unit and, following a CT scan, a diagnosis of phaeochromocytoma was made.

Which sign would most likely have been present in this patient as a result of her condition?

Answer 48

Diaphoresis
Correct. Well done! Phaeochromocytoma is a rare, catecholamine-secreting tumour. Increased secretion of adrenaline and noradrenaline from the tumour triggers the sympathetic nervous system ‘fight or flight’ response, causing an activation of sweat glands. Therefore diaphoresis (excessive sweating) can be a presenting sign.
Note on Signs and symptoms:
Signs and symptoms are abnormalities that can indicate a potential medical condition. Whereas a symptom is subjective, that is, apparent only to the patient (for example back pain or fatigue), a sign is any objective evidence of a disease that can be observed by others (for example a skin rash or lump).

Question 49

A 13 year old boy is referred to the paediatric unit after presenting with headaches, palpitations, diaphoresis, anxiety and recent weight loss. A 24 hour urine test reveals metanephrine production of 650 µmol/24 hours (normal: 0-3.7 µmol/24 hours).

What is the most likely diagnosis?

Answer 49

Phaeochromocytoma
Correct. Well done! Phaeochromocytoma is a rare tumour of chromaffin cells in the adrenal medulla. When a chromaffin cell tumour develops outside the adrenal gland, it is referred to as a paraganglioma. Both these types of neuroendocrine tumour produce massive amounts of catecholamines (adrenaline and noradrenaline) which result in the symptoms described in the question. The measurement of urine metanephrine is considered the best tool in the diagnosis of phaeochromocytoma.

Question 50

Approximately ~90% of the thyroid hormone secreted by the thyroid gland is in the form of T4. Most of this T4 is subsequently converted to T3 in the liver and kidneys. The biological activity of T3 is approximately 4 times greater than that that of T4.

What type of receptor do both these hormones bind to to elicit a cellular response?

Answer 50

nuclear

Question 50

Approximately ~90% of the thyroid hormone secreted by the thyroid gland is in the form of T4. Most of this T4 is subsequently converted to T3 in the liver and kidneys. The biological activity of T3 is approximately 4 times greater than that that of T4.

What type of receptor do both these hormones bind to to elicit a cellular response?

Answer 50

nuclear

Question 51

Thyroid hormones are fat soluble hormones and are mostly transported in plasma bound to protein. Which protein serves to transport thyroid hormone (T3 & T4) in plasma?

Answer 51

Thyroxine-binding globulin (TBG) binds & transports thyroid hormone in circulation. The proteins transthyretin and albumin also serve this purpose but the majority of thyroid hormone is transported by TBG.

Question 52

A 39 year old woman presents to her GP with cough and shortness of breath. On physical examination, a nodule was palpated in the middle portion her thyroid gland. A biopsy was taken on referral and histological examination revealed a medullary carcinoma. Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells.

Which substance is normally secreted by these cells?

Answer 52

Calcitonin
CORRECT. The Parafollicular (sometimes called C cells) are located in the spaces between thyroid follicles and secrete calcitonin. The follicular (NOT parafollicular) cells are arranged into spheres called thyroid follicles which are filled with colloid (a deposit of the protein thyroglobulin). Thyroid hormone is synthesised in and released from the thyroid follicles.

Question 53

Approximately ~90% of the thyroid hormone secreted by the thyroid gland is in the form of T4. Most of this T4 is subsequently converted to T3 in the liver and kidneys. The biological activity of T3 is approximately 4 times greater than that that of T4.

What is a biological effect of both these hormones?

Answer 53

Increase in the size of mitochondria
Correct. Thyroid hormone stimulates an increase in both the number and size of mitochondria in cells.

Question 54

A 43 year old woman presents to her GP complaining of feeling fatigued over the last couple of months, muscle aches and stiffness. The GP palpates a tender mass on the anterior aspect of the patient’s neck and orders a thryoid function test which tests positive for anti-thyroid antibodies. A diagnosis of Hashimoto’s thyroiditis was made and the patient is prescribed the drug levothyroxine.

What is the mode of action of this drug?

Answer 54

Binds to thyroid hormone receptors on DNA to modulate gene transcription
Correct. Well done! Thyroid hormones (and the drug levothyroxine) bind to thyroid hormone receptor on DNA to cause a conformational change in the receptor typically relieving repression of gene transcription.

Question 55

A 26 year old man is diagnosed with Hashimoto’s disease.

Which feature relates to this disease?

Answer 55

~6 times more common in women compared to men
Correct. In common with several other autoimmune diseases, Hashimoto’s disease is more common in women than men.

Question 56

~6 times more common in women compared to men
Correct. In common with several other autoimmune diseases, Hashimoto’s disease is more common in women than men.

Answer 56

~1%
CORRECT. The vast majority of thyroid hormone is bound to binding protein in plasma. It is only the free form however that is biologically active.

Question 57

A 56 year old woman visits her GP complaining of irritability, insomnia, excessive sweating and heart palpitations. Further investigations lead to a diagnosis of Graves’ disease.

Which drug could be used to treat this woman’s condition?

Answer 57

Carbimazole
Carbimazole is used to treat hyperthyroidism. Carbimazole is a pro-drug and is converted to its active form methimazole by the body. Methimazole prevents the enzyme thyroid peroxidase from coupling and iodinating tyrosine residues on thyroglobulin thus reducing the production of the thyroid hormones T3 and T4.

Question 58

What is the half life of thyroxine (T4) in plasma?

Answer 58

~5-7 days
Correct. The half-life of T4 is ~5-7 days; the half-life of T3 is lower at ~1 day.

Question 59

The parathyroid glands play a central role in calcium homeostasis by producing parathyroid hormone.

How do the cells in these glands sense plasma calcium concentration?

Answer 59

By G-protein coupled receptors than are activated by calcium
CORRECT. The calcium receptors on the parathyroid gland are G-protein coupled receptors. You will learn more about this class of receptor in the membranes and receptors unit.

Question 60

Parathyroid hormone is a hormone secreted by the parathyroid glands that regulates the serum calcium concentration through its effects on bone, kidney and the gastrointestinal tract.

How does this hormone exert its effects in the gastrointestinal tract?

Answer 60

Indirectly through promoting the formation of calcitriol

Question 61

calcitonin vs calcitriol

Answer 61

calcitriol helps increase blood calcium levels, and calcitonin helps decrease blood calcium levels

Question 62

Calcitonin is secreted by the parafollicular cells of the thyroid gland.

What is the action of this hormone in the gastrointestinal tract?

Answer 62

No effect
CORRECT. Calcitonin has no effect on the gastrointestinal tract. It is the hormone calcitriol that acts to increase the absorption of both calcium and phosphate in the gastrointestinal tract.

Question 63

A 47 year old woman visits her GP complaining of fatigue, bone pain, muscle soreness and feeling depressed. The GP sends a blood sample for analysis and this shows a serum calcium of 6 mmol/L (normal: 2.20 - 2.60 mmol/L). Subsequent investigations reveal that the woman has a parathyroid gland tumour that has resulted in secretion of excess parathyroid hormone.

What type of hormone is this?

Answer 63

Peptide hormone
CORRECT. Parathyroid hormone is a peptide hormone that is synthesized and secreted by the parathyroid gland in response to a drop in systemic calcium.

Question 64

Parathyroid hormone plays a key role in regulating calcium homeostasis.

What effects does this hormone have on plasma calcium and phosphate levels?

Answer 64

Decreased plasma phosphate increased plasma calcium
CORRECT. Parathyroid hormone stimulates osteoclast activity in bone resulting in the release of both calcium and phosphate. However, parathyroid hormone also stimulates the kidney to increase the reabsorption of calcium and decrease the reabsorption of phosphate. Since more phosphate is lost in urine than gained from bone mobilisation, the net effect of parathyroid hormone is to increase plasma calcium and decrease plasma phosphate. As well as its effects in bone and kidney, parathyroid hormone also has indirect effects on the GI tract by promoting the formation of calcitriol (the active form of vitamin D).

Question 65

A 14 year old boy competes in the 1500m race during his School sports day. After starting the race the concentration of ADP in his skeletal muscles radiply increases as a consequence of the ATP hydrolysis that is occurring to drive muscle contraction. This rise in ADP stimulates the activity of an enzyme to increase the rate of glycolysis in his muscles.

Which enzyme has been stimulated?

Answer 65

Phosphofructokinase
CORRECT. Phosphofructokinase, the key regulator of glycolysis is stimulated by high AMP and inhibited by high ATP.

Question 66

A 22 year old woman with type 1 diabetes mellitus self administers a subcutaneous injection of the hormone insulin.

What effect will this hormone have on the enzyme phosphofructokinase in her liver?

Answer 66

Increases activity
CORRECT. PFK is the rate limiting enzyme in glycolysis. Think of Insulin as the “hormone of plenty” and glucagon opposing the effects of insulin. If you have just had a meal then you would want to promote the utilisation of glucose to bring plasma glucose back down.