Nokea
Cortisol secretion is directly stimulated by:
- A. Aldosterone
- B. Prolactin
- C. ACTH
- D. CRH
Correct Answer: C
Rationale: Cortisol secretion is directly stimulated by adrenocorticotropic hormone (ACTH), which is produced and released by the anterior pituitary gland in response to corticotropin-releasing hormone (CRH) from the hypothalamus. ACTH acts on the adrenal cortex to stimulate the production and release of cortisol. Aldosterone is another hormone produced by the adrenal cortex, but it is not directly involved in the stimulation of cortisol secretion. Prolactin is a hormone produced by the pituitary gland that plays a role in lactation, not cortisol secretion. High blood potassium levels can stimulate aldosterone secretion but do not directly stimulate cortisol secretion.
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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.
Increased gonadal production of oestrogen is seen in:
- A. Third trimester of pregnancy
- B. Congenital adrenal hyperplasia
- C. Polycystic ovarian disease
- D. Testicular feminization syndrome
Correct Answer: C
Rationale: Polycystic ovarian disease, also known as polycystic ovary syndrome (PCOS), is a common endocrine disorder characterized by increased levels of androgens (male hormones) and disrupted estrogen production in the ovaries. The hormonal imbalance seen in PCOS leads to increased gonadal production of estrogen. This condition is often associated with symptoms such as irregular menstrual cycles, infertility, acne, and excess facial or body hair growth. In contrast, the other options do not typically involve increased gonadal production of estrogen as seen in PCOS.
Which of the following tests should be used to make the diagnosis of Cushing's syndrome?
- A. 24-hour urine free cortisol
- B. Corticotropin-releasing hormone (CRH) level at 8 a.m.
- C. Inferior petrosal venous sampling
- D. Overnight 1-mg dexamethasone suppression test
Correct Answer: D
Rationale: The overnight 1-mg dexamethasone suppression test is commonly used as an initial screening test for Cushing's syndrome. In this test, a patient takes 1 mg of dexamethasone orally at 11 p.m., and their serum cortisol level is measured the next morning. In patients with Cushing's syndrome, the cortisol levels will not be suppressed by the dexamethasone due to the presence of excessive cortisol production.
Hypocalcemia is produced by all except:
- A. Hysterical hypoventilation
- B. Acute pancreatitis
- C. Chronic renal failure
- D. Osteomalacia
Correct Answer: D
Rationale: Osteomalacia is a condition in which there is a softening of the bones due to a deficiency in vitamin D or calcium. It is not a cause of hypocalcemia, as it is a result of low levels of calcium in the bloodstream. The other options listed are potential causes of hypocalcemia:
In males which hormone stimulates Leydig cells to produce testosterone?
- A. Follicle stimulating hormone (FSH)
- B. Luteinizing hormone (LH)
- C. hormone
- D. insipidus
Correct Answer: B
Rationale: In males, Leydig cells in the testes are stimulated to produce testosterone by luteinizing hormone (LH). LH is produced by the anterior pituitary gland and acts on the Leydig cells to promote the synthesis and release of testosterone. This hormone plays a crucial role in male reproductive function and the development of masculine characteristics. Follicle stimulating hormone (FSH) plays a role in spermatogenesis in males but does not directly stimulate Leydig cells to produce testosterone.