Pre Clinical Medical Science SBAs
Pre Clin Endocrine: (50 questions)

Questions

• 1
  Which vessels lie immediately posterolateral to the thyroid gland?
  Difficulty: Medium     Topic: Thyroid relations 1
  a

  Common carotid artery and internal jugular vein

  b

  Common carotid artery and external jugular vein

  c

  External carotid artery and external jugular vein

  d

  Internal carotid artery and external jugular vein

  e

  Internal carotid artery and internal jugular vein
  Explanation: The carotid sheath lies immediately posterior and lateral to the thyroid gland. It contains the internal jugular vein, descending vagus nerve and the common carotid (or the internal carotid artery). The common carotid divides into the internal & external carotid at the level of the top of the thyroid cartilage therefore at the level of the thyroid the sheath contains the common carotid.
• 2
  Where does parathyroid hormone act?
  Difficulty: Easy     Topic: Parathyroid hormone 1
  a

  Kidney and bone

  b

  Kidney, bone and intestine

  c

  Kidney, bone and muscle

  d

  Kidney, bone and parathyroid gland

  e

  Kidney, intestine and thyroid
  Explanation: Parathyroid hormone (PTH) acts on bone to stimulate reabsorption which releases calcium and phosphate. In the kidney PTH increases reabsorption of calcium, promotes phosphate excretion and increases synthesis of 1-alpha-hydroxylase - the enzyme needed for activation of vitamin D.
• 3
  What is the overall effect of of parathyroid hormone on bone?
  Difficulty: Easy     Topic: Parathyroid hormone 2
  a

  Increase osteoblast activity

  b

  Increase chondrocyte proliferation

  c

  Increase osteoclast activity

  d

  Reduce chondroblast activity

  e

  Reduce osteoclast proliferation
  Explanation: PTH promotes bone reabsorption by increasing the activity of osteoclasts, however this is done by binding to receptors on osteoblasts. In response, osteoblasts then secrete cytokines that increase osteoclast activity. Osteoclasts are multinucleate cells that are involved in bone remodelling. Osteoblasts form new bone. Chondrocytes (maintain cartilage) and chondroblasts (form new cartilage) are little affected by PTH.
• 4
  What is the role of 1-alpha-hydroxylase?
  Difficulty: Medium     Topic: 1-alpha-hydroxylase
  a

  Activate parathyroid hormone

  b

  Activate vitamin D

  c

  Hydrolyse 25-OH-D3

  d

  Increase calcium channel activity

  e

  Synthesise calcium-binding protein
  Explanation: Vitamin D is synthesised de novo in the skin or absorbed in the bowel as inactive D3. It undergoes two hydroxylation reactions to become active. Firstly in the liver to 25-OH-D3, and then in the kidney to 1,25-(OH)2-D3. The latter is catalysed by 1-alpha-hydroxylase and is the rate-limiting step. Active vitamin D regulates bone turnover, increases calcium reabsorption in the kidney and the bowel.
• 5
  What is the most common cause of primary hyperparathyroidism?
  Difficulty: Easy     Topic: Hyperparathyroidism
  a

  Benign parathyroid adenoma

  b

  Increased vitamin D production

  c

  Malignant parathyroid tumour

  d

  Parathyroid hyperplasia

  e

  Renal failure
  Explanation: Primary hyperparathyroidism occurs due to an intrinsic pathology of the parathyroid gland, which is most often a benign adenoma. Hyperplasia and malignant tumours are much more rare. Renal failure is a cause of secondary hyperparathyroidism. Increased active vitamin D can be secondary to hyperparathyroidism.
• 6
  How do glucocorticoids exert negative feedback on ACTH secretion?
  Difficulty: Easy     Topic: HPA axis
  a

  ACTH inhibits CRH secretion

  b

  ACTH inhibits further release of itself

  c

  Aldosterone inhibits ACTH secretion

  d

  Cortisol inhibits ACTH and CRH secretion

  e

  Cortisol inhibits ACTH secretion
  Explanation: Cortisol, produced by the zona fasiculata of the adrenal cortex, is the main glucocorticoid. Cortisol exerts the negative feedback of this system; most at the level of the pituitary (by reducing ACTH) but also at the hypothalamus to reduce CRH.
• 7
  What is the definition of Cushing disease?
  Difficulty: Hard     Topic: Cushing disease
  a

  Features from excess glucocorticoid

  b

  Features from excess glucocorticoid due to a ACTH-secreting pituitary tumour

  c

  Features from excess mineralocorticoid

  d

  Features from lack of glucocorticoid

  e

  Features from lack of glucocorticoid due to TB-adrenalitis
  Explanation: Cushing syndrome is the constellation of signs and symptoms associated with glucocorticoid excess. Cushing disease is when the syndrome occurs due to a pituitary adenoma secreting ACTH. Excess mineralocorticoid is hyperaldosteronism, which may be due to a tumour, called Conn syndrome. Glucocorticoid lack is Addison syndrome, and Addison disease if due to TB-adrenalitis.
• 8
  How does cortisol exert it’s actions?
  Difficulty: Easy     Topic: Cortisol
  a

  Binding a G-protein coupled receptor

  b

  Binding a tyrosine-kinase receptor

  c

  Binding an ion channel

  d

  Binding an internal receptor for transcription effects

  e

  Binds directly to DNA
  Explanation: All steroid hormones act by ligating intracellular receptors that then bind DNA promotor regions to affect gene transcription.
• 9
  What is the role of glucocorticoids in the immune system?
  Difficulty: Medium     Topic: Glucocorticoids
  a

  Cause granulocyte necrosis

  b

  Increase B-cell proliferation

  c

  Increase mast cell activity

  d

  Inhibit macrophage killing mechanisms

  e

  Reduce lymphocyte proliferation
  Explanation: Cortisol is a potent anti-inflammatory hormone. It primarily suppresses the activity of lymphocytes: reduces cytokine secretion and inhibits their proliferation. High doses of potent exogenous glucocorticoids are used in chemotherapy against lymphoproliferative disease.
• 10
  What serum electrolyte abnormality is a stimulus for aldosterone release?
  Difficulty: Easy     Topic: Aldosterone 1
  a

  Hypercalcaemia

  b

  Hyperkalaemia

  c

  Hypernatraemia

  d

  Hypokalaemia

  e

  Hyponatraemia
  Explanation: Aldosterone is released in response to several factors: angiotensin-II, hyperkalaemia and small amounts due to ACTH. Aldosterone promotes secretion of potassium into the tubular lumen, which lowers its serum concentration.
• 11
  How is mineralocorticoid secretion affected in pituitary failure?
  Difficulty: Medium     Topic: Aldosterone 2
  a

  Increased

  b

  Reduced but compensated by ACTH

  c

  Reduced but compensated by cortisol

  d

  Reduced to zero

  e

  Unaffected
  Explanation: Aldosterone secretion is predominantly controlled by the renin-angiotensin system and serum potassium concentration rather than ACTH. Therefore in primary adrenal failure mineralocorticoids, unlike glucocorticoids, usually do not need to be replaced.
• 12
  Which hormone ratio is increased in cases of a tumour secreting aldosterone?
  Difficulty: Hard     Topic: Aldosterone 3
  a

  ACTH : cortisol ratio

  b

  Aldosterone : renin ratio

  c

  Cortisol : aldosterone ratio

  d

  DHEA : aldosterone ratio

  e

  Renin : aldosterone ratio
  Explanation: An aldosterone-secreting tumour (Conn syndrome) causes aldosterone to be released in the absence of renin-stimulation. Therefore aldosterone:renin ratio rises.
• 13
  How does the thyroid gland develop?
  Difficulty: Easy     Topic: Thyroid embryology
  a

  Ascent of endoderm from pharyngeal arches

  b

  Coalescence of neural crest cells

  c

  Descend of endoderm from the tongue

  d

  Folding of neural tube ectoderm

  e

  Migration of lateral plate mesoderm
  Explanation: The thyroid is formed from endoderm in the tongue. It descends down through the neck from a point 2/3rd back on the tongue called the foramen caecum (the midpoint of the sulcus terminalis). The thyroid gland moves from here to its location anterior to the trachea via the thyroglossal duct.
• 14
  What is the mechanism of action of thyroperoxidase and carbimazole?
  Difficulty: Hard     Topic: Anti-thyroid drugs
  a

  Blockade of TRH receptor

  b

  Blockade of TSH receptor

  c

  Follicular cell apoptosis

  d

  Inhibition of iodine uptake

  e

  Inhibition of thyroperoxidase
  Explanation: Carbimazole and propylthiouracil (PTU) are drugs that inhibit the iodination of thyroglobulin by the enzyme thyroperoxidase. This prevents the formation of T3 and T4. Radio-iodine is used to cause thyroid apoptosis in resistant cases of hyperthyroidism.
• 15
  Which nerve runs posteromedial to the thyroid gland?
  Difficulty: Easy     Topic: Thyroid relations 2
  a

  Accessory nerve

  b

  External superior laryngeal nerve

  c

  Internal superior laryngeal nerve

  d

  Long thoracic nerve of Bell

  e

  Recurrent laryngeal nerve
  Explanation: The recurrent laryngeal nerve is a branch of the vagus nerve that arises in the thorax and ascends in the neck to supply the intrinsic muscle of the larynx (except for cricothyroid). On the right, the vagus gives off the recurrent laryngeal nerve under the subclavian artery. On the left, the recurrent laryngeal arises from under the aortic arch. There is risk of damage to this nerve during thyroid surgery.
• 16
  From which vessel does the superior thyroid artery branch off?
  Difficulty: Easy     Topic: Thyroid blood supply
  a

  Thyroid blood supply

  b

  Facial artery

  c

  Internal carotid artery

  d

  Subclavian artery

  e

  Thyrocervical trunk
  Explanation: The thyroid is supplied by the superior and inferior thyroid arteries that are branches of the external carotid artery and thyrocervical trunk respectively. The thyrocervical trunk is a branch off the subclavian artery that also supplies the neck and the vertebral artery.
• 17
  Which vessel is most commonly at risk during a tracheostomy procedure?
  Difficulty: Hard     Topic: Tracheostomy
  a

  Inferior thyroid artery

  b

  Inferior thyroid vein

  c

  Middle thyroid vein

  d

  Superior thyroid artery

  e

  Superior thyroid vein
  Explanation: A tracheostomy is performed by making an incision through the tracheal cartilage inferior to the thyroid gland. The inferior thyroid vein runs over the anterior of the trachea down to the brachiocephalic vein, thus posing a risk. The middle and superior thyroid veins pass laterally into to internal jugular vein. The inferior thyroid artery also passes laterally away from the trachea.
• 18
  What is the role of the thyroid cells that lie between follicles?
  Difficulty: Easy     Topic: Thyroid cells
  a

  Detect the need for thyroid hormones

  b

  Iodine uptake

  c

  Secrete calcitonin

  d

  Secrete parathyroid hormone

  e

  Synthesis of T4
  Explanation: The thyroid contains two cell types: follicular cells (that produce thyroid hormones) and parafollicular cells, which produce the hormone calcitonin. Calcitonin inhibits osteoclasts and acts to lower serum calcium levels. In overall calcium metabolism it has a minor role in comparison to parathyroid hormone and vitamin D.
• 19
  What is the embryological origin of the inferior parathyroid glands?
  Difficulty: Hard     Topic: Parathyroid embryology
  a

  3rd pharyngeal arch

  b

  3rd pharyngeal pouch

  c

  4th pharyngeal arch

  d

  4th pharyngeal pouch

  e

  Endoderm in the tongue
  Explanation: The inferior parathyroid glands come from the 3rd pharyngeal pouch. They descend past the superior parathyroid glands, which are derived from the 4th pharyngeal pouch. They are composed of endoderm.
• 20
  What are the names of the two cell types present in the parathyroid glands?
  Difficulty: Medium     Topic: Parathyroid cells
  a

  Chief cells and follicular cells

  b

  Chief cells and oxyphil cells

  c

  Chief cells and parietal cells

  d

  Follicular cells and parafollicular cells

  e

  Parafollicular cells and oxyphil cells
  Explanation: The parathyroid glands contain chief cells, which produce parathyroid hormone and detect serum calcium levels. [Similarly named but different in function to the gastric chief cells.] The other cells are called oxyphil cells, their function is unknown. Follicular and parafollicular cells are in the thyroid.
• 21
  What is the embryological origin of the adrenal medulla?
  Difficulty: Hard     Topic: Adrenal medulla
  a

  Extra-gastrointestinal endoderm

  b

  Lateral plate mesoderm

  c

  Neural crest cells

  d

  Neural tube budding

  e

  Para-axial mesoderm
  Explanation: The adrenal medulla is made from neural crest cells, which are formed from budding off of the neural plate during neuralation. The adrenal cortex is made from lateral plate mesoderm.
• 22
  What structure lies lateral to the superior pole of the right adrenal gland?
  Difficulty: Easy     Topic: Adrenal relations
  a

  IVC

  b

  Liver

  c

  Pancreas

  d

  Right kidney

  e

  Spleen
  Explanation: The adrenal glands lie superomedial on the kidneys. Immediately lateral to the superior pole of the left adrenal is the liver; anteromedial is the IVC. Lateral to the inferior pole of the adrenal gland is the kidney itself. The spleen and pancreas lie close to the right adrenal gland.
• 23
  Where does the superior adrenal artery arise from?
  Difficulty: Medium     Topic: Adrenal blood supply
  a

  Abdominal aorta

  b

  Coeliac trunk

  c

  Inferior phrenic artery

  d

  Renal artery

  e

  Superior phrenic artery
  Explanation: The adrenal glands are supplied by three arteries. The superior adrenal artery from by inferior phrenic, the middle adrenal artery directly off the abdominal aorta, and the inferior adrenal off the renal artery. There is one adrenal vein that drains into the IVC on the right and renal vein on the left.
• 24
  Which of the following area – hormone pairs is correct?
  Difficulty: Easy     Topic: Adrenal layers
  a

  Zona fasiculata - aldosterone

  b

  Zona glomerulosa - aldosterone

  c

  Zona glomerulosa - cortisol

  d

  Zona reticularis - aldosterone

  e

  Zona reticularis - cortisol
  Explanation: There are three layers in the adrenal cortex, from superficial to deep: zona glomerulosa, zona fasiculata and zona reticularis. These secrete mineralocorticoids (aldosterone), glucocorticoids (cortisol) and androgens (DHEA and androstenedione) respectively.
• 25
  What structure lies immediately superior to the pituitary gland?
  Difficulty: Easy     Topic: Pituitary relations
  a

  Cavernous sinus

  b

  Cranial nerve III

  c

  Cribiform plate

  d

  Mamillary bodies

  e

  Optic chiasm
  Explanation: The pituitary gland sits in the sella turcia of the sphenoid bone. Immediately superior are the optic nerve fibres from the nasal retina that cross over - known as the optic chiasm. Cranial nerves III, IV, V and VI run in the cavernous sinus lateral to the pituitary gland. The mamillary bodies lie posterior to the pituitary in the temporal lobe and the cribiform plate in anterosuperior in the ethmoid bone.
• 26
  What is the most common side-effect of metformin?
  Difficulty: Easy     Topic: Metformin
  a

  Accelerated cardiovascular disease

  b

  Diarrhoea

  c

  Hypoglycaemia

  d

  Lactic acidosis

  e

  Myalgia
  Explanation: Metformin is a biguanide that increases insulin sensitivity by: increasing glucose uptake, reducing gluconeogenesis and increasing glycogen synthesis. It most commonly causes diarrhoea and dyspepsia. It reduces cardiovascular disease progression. It extremely rarely causes hypoglycaemia. Lactic acidosis is a rare, serious side-effect. Myalgia is infrequently reported.
• 27
  What molecule is produced as a by-product of insulin synthesis?
  Difficulty: Medium     Topic: Insulin
  a

  A-chain

  b

  B-protein

  c

  C-peptide

  d

  C-reactive protein

  e

  Protein C
  Explanation: Insulin is made from pre-pro-insulin, which is cleaved first to pro-insulin, then insulin. In this last stage a peptide chain is produced called C-peptide, which is a marker of insulin synthesis. The A- and B-chains comprise the final insulin molecule. C-reactive protein is an acute phase reactant. Protein C is involved in antithrombotic mechanisms.
• 28
  What is precursor molecule for synthesis of all steroid hormones?
  Difficulty: Easy     Topic: Steroid synthesis 1
  a

  Androstenedione

  b

  Cholesterol

  c

  Long-chain hydrocarbons

  d

  Pregnenolone

  e

  Tyrosine
  Explanation: All steroid hormones are synthesised from cholesterol. The first step is always conversion to pregnenolone. Androstenedione is a sex steroid precursor to oestrogens. Long-chain hydrocarbons are fats used for energy. Tyrosine is an amino acid used to make catecholamines and thyroid hormones.
• 29
  What is the rate limiting step of steroid hormone synthesis?
  Difficulty: Hard     Topic: Steroid synthesis 2
  a

  Steroid synthesis 2

  b

  Moving pregnenolone into the endoplasmic reticulum

  c

  Post-synthesis modification

  d

  Secretion of the final product

  e

  Synthesis of DHEA
  Explanation: Cholesterol is first converted into pregnenolone in the mitochondria, but then must be moved to the endoplasmic reticulum for further conversion. This process is regulated by a protein called STAR that is induced by ACTH. Post-synthesis modification and secretion and not rate limiting steps. DHEA is a specific sex steroid and not a general rate limiting step.
• 30
  21-hydroxylase is required for the synthesis of which hormones?
  Difficulty: Hard     Topic: Steroid synthesis 3
  a

  Aldosterone and cortisol

  b

  DHEA and androstenedione

  c

  Oestrogens

  d

  Pregnenolone

  e

  Testosterone
  Explanation: 21-hydroxylase is an enzyme expressed in the adrenal cortex that is necessary for the synthesis of precursors to aldosterone and cortisol. Deficiency of this enzyme results in a lack of mineralocorticoids and glucocorticoids with an excess of sex steroids (DHEA, androstenedione, oestrogens, testosterone). Pregnenolone is a precursor to all steroid hormones.
• 31
  Where does iodination of thyroglobulin occur?
  Difficulty: Medium     Topic: Thyroid hormones 1
  a

  Cytosol

  b

  Follicle colloid

  c

  Lysosomes

  d

  Rough endoplasmic reticulum

  e

  Smooth endoplasmic reticulum
  Explanation: Thyroglobulin is a large protein synthesised in thyroid follicular cells and exocytosed into colloid follicles. Thyroid peroxidase catalyses iodination of tyrosine residues on thyroglobulin in the follicle lumen. Thyroglobulin is hydrolysed inside follicular cells after fusion with lysosomes.
• 32
  How is most triiodothyronine (T3) produced?
  Difficulty: Easy     Topic: Thyroid hormones 2
  a

  Deiodination of T4 in peripheral tissues

  b

  Deiodination of T4 in the thyroid

  c

  Hydrolysis of thyroglobulin

  d

  Iodination of di-iodothyronine in circulation

  e

  Proteolysis of thyroglobulin
  Explanation: Most T3 is produced by the action of de-iodinases in the liver that act on circulating T4. The thyroid produces 95% T4 (and 5% T3) by proteolysis of thyroglobulin. Di-iodothyronine is iodinated on thyroglobulin in thyroid follicles.
• 33
  In the secretion of insulin, which ion channels close to cause beta-cell depolarisation?
  Difficulty: Medium     Topic: Insulin secretion 1
  a

  ADP-sensitive Na+

  b

  ATP-sensitive K+

  c

  Glucose-sensitive Na+

  d

  Voltage-gated Ca2+

  e

  Voltage-gated K+
  Explanation: Secretion of insulin is predominantly dependent on circulating glucose levels. High glucose increases ATP production, which causes ATP-sensitive K+ channels to close and results in beta-cell depolarisation. This then activates voltage-gated calcium channels and the calcium entry causes exocytosis of vesicles containing insulin.
• 34
  After eating, how many peaks of insulin secretion are there?
  Difficulty: Easy     Topic: Insulin secretion 2
  a

  1

  b

  2

  c

  3

  d

  4

  e

  5
  Explanation: There are two phases of insulin secretion in the post-prandial state. There is an early, high and short lasting peak in insulin levels soon after eating. Following this there is a more prolonged phase of secretion. In addition, there is always a basal level of insulin secretion, even in the fasting state.
• 35
  Which HLA groups are associated with type 1 diabetes mellitus?
  Difficulty: Easy     Topic: Type 1 diabetes
  a

  B2

  b

  B27

  c

  B8

  d

  DR14

  e

  DR3/4
  Explanation: Type 1 diabetes mellitus is a autoimmune disease (AID) caused by destruction of the beta-cells in the pancreatic islets. It is associated with many other AID through HLA-DR3 or -DR4 e.g. pernicious anaemia, vitiligo, autoimmune hepatitis. B27 is associated with seronegative arthritidies e.g. psoriasis.
• 36
  What feature is most likely to indicate type 2 diabetes rather than type 1?
  Difficulty: Easy     Topic: Type 2 diabetes
  a

  Absence of ketones

  b

  Family history

  c

  Infections

  d

  Obesity

  e

  South East Asian ethnicity
  Explanation: Only a small amount of insulin is required to suppress ketone synthesis therefore patients with type 2 diabetes mellitus (DM) almost never produce ketones. Family history is common in both type 1 and 2. Obesity and South East Asian ethnicity are more common in type 2 these patients may still get type 1. Increased infections is a symptom of all DM.
• 37
  How does insulin affect metabolism in the liver?
  Difficulty: Easy     Topic: Insulin
  a

  Increases conversion of alanine to glucose

  b

  Increases glyogenesis

  c

  Increases lipolysis

  d

  Increases ketogenesis

  e

  Reduces gluconeogenesis
  Explanation: Insulin is the body's main anabolic hormone - it promotes storage of protein, adipose and glycogen whilst inhibiting their breakdown. It also reduces the generation of new glucose from other substrates (gluconeogenesis e.g. alanine to glucose). Insulin avidly blocks ketogenesis.
• 38
  How do sulphonylureas reduce blood glucose?
  Difficulty: Easy     Topic: Sulphonylureas
  a

  Increase DPP-4 activity

  b

  Increase insulin release

  c

  Increase peripheral uptake of glucose

  d

  Reduce glucagon production

  e

  Reduce gluconeogenesis
  Explanation: Sulphonylureas are oral hypoglycaemic agents that bind a specific receptor on beta-cells to causes depolarisation and stimulate insulin release. Increasing DPP-4 would reduce insulin secretion. Metformin increases peripheral uptake. GLP-1 reduces glucagon secretion. Insulin reduces gluconeogenesis.
• 39
  What is the name of the precursor molecule that ACTH is cleaved from?
  Difficulty: Easy     Topic: ACTH
  a

  Cortisol

  b

  Gamma-MSH

  c

  Pre-pro-ACTH

  d

  Pro-ACTH

  e

  Pro-opiomelanocortin
  Explanation: POMC (pro-opiomelanocortin) is a large precursor molecule synthesised in the pituitary. In response to corticotroph releasing hormone (from the hypothalamus) it is cleaved into ACTH (adrenocorticotrophic hormone), which stimulates cortisol release from the adrenals. When cleaved, POMC also produces gamma-melanocyte stimulating hormone (MSH). There is no pro- or pre-pro-ACTH.
• 40
  Where is GLP-1 released from?
  Difficulty: Easy     Topic: Incretin system 1
  a

  Alpha-cells in pancreatic islets

  b

  Colonic APUD cells

  c

  Duodenal L-cells

  d

  Gastric chief cells

  e

  Pancreatic acinar cells
  Explanation: Glucagon-like peptide-1 (GLP-1) is a hormone released by duodenal L-cells in response to intraluminal carbohydrate. It is the most important of the 'incretins'. GLP-1 has 4 main actions: increase insulin release, reduce glucagon release, slow gastric emptying and increase satiety.
• 41
  What is the role of dipeptidylpeptidase-4 (DPP-4)?
  Difficulty: Easy     Topic: Incretin system 2
  a

  Activate GLP-1

  b

  Break down GLP-1

  c

  Break down insulin

  d

  Increase insulin release

  e

  Synthesise GLP-1
  Explanation: DPP-4 is a hormone that catalyses proteolysis of GLP-1, therefore reducing it's actions. Over 90% of all secreted GLP-1 is broken down before it reaches the pancreatic islets. GLP-1 is already active. Insulin is excreted through the kidneys mostly intact. GLP-1 increases insulin release.
• 42
  What drug is a mimetic of GLP-1?
  Difficulty: Hard     Topic: Incretin system 3
  a

  Acarbose

  b

  Exenatide

  c

  Glargine

  d

  Repaglinide

  e

  Sitagliptin
  Explanation: Exenatide is a drug that mimics the action of GLP-1. It is resistant to breakdown by DPP-4 therefore stays in circulation and exerts its actions. Acarbose inhibits alpha-glucosidase, which is needed for absorption of glucose. Glargine is a form of long-acting insulin. Repaglinide is a short-acting drug that increases insulin secretion, but is not a sulphonylurea. Sitagliptin inhibits DPP-4, therefore increases the effect of endogenous GLP-1.
• 43
  What is the role of leptin?
  Difficulty: Easy     Topic: Leptin
  a

  Increase appetite

  b

  Increase basal metabolic rate

  c

  Signal increased lipolysis

  d

  Signal raised adipose stores

  e

  Augments ghrelin release
  Explanation: Leptin is the most important hormone in signalling adipose stores. It is released by adipocytes that are laden with stored triglycerides therefore increases in proportion with fat stores. It acts to reduce appetite in an attempt to reverse the excess adipose stores. Ghrelin is released by the stomach during fasting and stimulates hunger.
• 44
  Which two hormones are produced by the posterior pituitary?
  Difficulty: Easy     Topic: Posterior pituitary
  a

  ADH and oxytocin

  b

  ADH and TRH

  c

  Dopamine and oxytocin

  d

  Prolactin and ADH

  e

  Prolactin and oxytocin
  Explanation: The posterior pituitary (neurohypophysis) secretes ADH (anti-diuretic hormone) and oxytocin. Both are synthesised in the hypothalamus and travel through neurones to the posterior from where they are secreted. ADH increases water reabsorption in the renal collecting ducts. Oxytocin causes contraction of smooth muscle in breast ductules.
• 45
  What hormone released by the hypothalamus negatively regulates pituitary secretion of prolactin?
  Difficulty: Easy     Topic: Prolactin 1
  a

  Dopamine

  b

  Ghrelin

  c

  IGF-1

  d

  Lactoferrin

  e

  Somatostatin
  Explanation: Prolactin secretion by the anterior pituitary is inhibited by dopamine, released by the hypothalamus. Oestrogen and progesterone during pregnancy increase prolactin. Ghrelin is released by the stomach in response to hunger and increases growth hormone (GH) release. Insulin-like growth factor-1 (IGF-1) is made by the liver in response to GH. Lactoferrin is an enzyme is saliva. Somatostatin inhibits GH release.
• 46
  What is the function of prolactin?
  Difficulty: Medium     Topic: Prolactin 2
  a

  Contraction of breast ductules

  b

  Increase gonadotrophin levels

  c

  Increased milk production in breast tissue

  d

  Increase uptake of triacylglycerides

  e

  Stimulate adipose hyperplasia
  Explanation: Prolactin increases milk production in breast acinar cells and stimulates hyperplasia of breast tissue. Oxytocin causes ductule contraction for milk expression. None of the other statements are correct.
• 47
  How does growth hormone exert most of its action?
  Difficulty: Easy     Topic: Growth hormone
  a

  By increasing IGF-1 release

  b

  By increasing somatostatin release

  c

  By suppressing adrenaline release

  d

  Through inhibition of ghrelin

  e

  Through the growth hormone receptor
  Explanation: Growth hormone (released by the anterior pituitary) binds to its receptor on hepatocytes, which secrete insulin-like growth factor-1 (IGF-1). IGF-1 binds a specific receptor on cells to cause: bone growth, soft tissue hyperplasia and metabolic effects. Somatostatin inhibits GH release. GH and adrenaline augment each other’s metabolic actions by increase glycolysis and lipolysis. Ghrelin stimulates GH release.
• 48
  What metabolic disorder may patients with acromegaly develop?
  Difficulty: Easy     Topic: Acromegaly
  a

  Addison disease

  b

  Diabetes

  c

  Hypercalcaemia

  d

  Hypoglycaemia

  e

  Hypokalaemia
  Explanation: Acromegaly is the clinical condition caused by excess growth hormone, almost always due to a benign tumour. Growth hormone stimulates glycolysis, inhibits glycogenesis and increases gluconeogenesis - similar actions to glucagon and adrenaline; antagonising insulin. The effect is a form of non-insulin dependent diabetes mellitus.
• 49
  What hormone profile would be expected in primary hyperthyroidism?
  Difficulty: Easy     Topic: Hyperthyroidism
  a

  High TRH, high TSH, low T4

  b

  High TRH, low TSH, low T4

  c

  Low TRH, high TSH, high T4

  d

  Low TRH, low TSH, high T4

  e

  Low TRH, Low TSH, low T4
  Explanation: In primary hyperparathyroidism, there is excess production of T3 and T4 by the thyroid gland. T3 exerts most of the negative feedback by the thyroid hormones at both the pituitary (causing low TSH) and hypothalamus (causing low TRH). High TSH, high TRH and low T4 would be expected in primary hypothyroidism.
• 50
  What is the underlying pathology in Graves’ disease?
  Difficulty: Medium     Topic: Graves’ disease
  a

  Antibody-mediated follicular cell necrosis

  b

  Blocking antibodies against T3-receptor

  c

  Blocking antibodies against TSH-receptor

  d

  Stimulating antibodies against T3-receptor

  e

  Stimulating antibodies against TSH-receptor
  Explanation: Graves’ disease is an autoimmune condition that causes hyperthyroidism due to production of antibodies directed against the TSH receptor. When these antibodies bind they activate the receptor and this stimulates thyroid hyperplasia with increased T3/4 production. Hashimoto thyroiditis is caused by antibodies that result in follicular cell apoptosis/necrosis.