Nokea
Which one of the following statements describes the underlying pathology of Grave's disease?
- A. An autoimmune disease directed against thyroid stimulating hormone (TSH) receptors. The autoantibodies stimulate the TSH receptors causing increased T3 and T4 production.
- B. Inflammation of the thyroid gland due to lymphocytic infiltration causes the stored thyroid hormones to be released into the circulation leading to hyperthyroidism.
- C. Consumption of ground beef which has been contaminated with thyroid tissue. The thyroid tissue contains metabolically active thyroid hormones which causes hyperthyroidism.
- D. A benign tumour of the thyroid gland which produces excessive amounts of thyroid hormones.
Correct Answer: A
Rationale: Graves' disease is an autoimmune disorder where autoantibodies, known as thyroid-stimulating immunoglobulins (TSIs) or thyroid-stimulating antibodies (TSAs), bind to and stimulate the thyroid-stimulating hormone (TSH) receptors on thyroid follicular cells. This leads to increased production and secretion of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), causing hyperthyroidism. The autoantibodies essentially mimic the action of TSH, resulting in excess thyroid hormone release and manifestation of hyperthyroid symptoms. This underlying pathology of Graves' disease is distinct from other causes of hyperthyroidism, making choice A the correct statement.
You may also like to solve these questions
Which of the following is not a neuromuscular feature of thyrotoxicosis?
- A. Myasthenic syndrome
- B. Brisk knee jerk
- C. Hypokalaemic periodic paralysis
- D. Hyperkinesia
Correct Answer: A
Rationale: Thyrotoxicosis typically presents with hypermetabolism and various neuromuscular manifestations. Myasthenic syndrome, which involves muscle weakness and fatigability, is not a common neuromuscular feature of thyrotoxicosis. Instead, manifestations such as brisk knee jerk reflexes, hypokalaemic periodic paralysis (due to shifts in potassium levels), and hyperkinesia (excessive movement) are more commonly observed in patients with thyrotoxicosis. Myasthenic syndrome is more commonly associated with autoimmune disorders affecting the neuromuscular junction, such as myasthenia gravis.
Which of the following does the adrenal cortex produce?
- A. Adrenaline
- B. Aldosterone
- C. Cortisol
- D. Noradrenaline
Correct Answer: B
Rationale: The adrenal cortex is the outer region of the adrenal glands and is responsible for producing several hormones, including aldosterone. Aldosterone is a mineralocorticoid hormone that plays a crucial role in regulating electrolyte balance, particularly sodium and potassium, in the body. It helps maintain blood pressure and fluid balance by acting on the kidneys to reabsorb sodium and water while excreting potassium in the urine. Adrenaline and noradrenaline (also known as epinephrine and norepinephrine) are produced by the adrenal medulla, which is the inner region of the adrenal glands. Cortisol is another hormone produced by the adrenal cortex, but aldosterone specifically regulates electrolyte balance.
All of the following would be expected to increase prolactin levels except:
- A. Chest wall trauma
- B. Hyperthyroidism
- C. Pregnancy
- D. Renal failure
Correct Answer: B
Rationale: Prolactin levels can be increased by various factors, including chest wall trauma, pregnancy, and renal failure. However, hyperthyroidism is not typically associated with elevated prolactin levels. In fact, hyperthyroidism is more commonly associated with decreased levels of prolactin due to the inhibitory effect of thyroid hormones on prolactin secretion. Therefore, all of the options except for hyperthyroidism would be expected to increase prolactin levels.
Acromegaly is associated with all of the following except:
- A. Acanthosis nigricans
- B. Fibromata mollusca
- C. Micrognathia
- D. Cardiomegaly
Correct Answer: C
Rationale: Acromegaly is a disorder caused by excessive growth hormone production after the closure of the epiphyses (growth plates) in bones, leading to abnormal growth of tissues and organs. The following options are associated with acromegaly:
All the following are risk factors for the development of osteoporotic fractures except
- A. African race
- B. Current cigarette smoking
- C. Female sex
- D. Physical inactivity
Correct Answer: A
Rationale: While African race is considered a protective factor against the development of osteoporosis due to higher peak bone mass and lower fracture rates compared to other races, the other factors listed (current cigarette smoking, female sex, and physical inactivity) are all established risk factors for the development of osteoporotic fractures. African-American individuals, in general, have a lower risk of osteoporosis and fractures compared to Caucasians and Asians.