Nokea
What is the most common cause for the overproduction of growth hormone in acromegaly?
- A. Hypothalamic lesion
- B. Hyperplasia of the pituitary stalk
- C. Pituitary lesion
- D. Pituitary adenoma
Correct Answer: D
Rationale: Acromegaly is typically caused by the overproduction of growth hormone (GH) by the pituitary gland. In around 95% of cases, this overproduction is due to the presence of a non-cancerous tumor called a pituitary adenoma. These adenomas are benign, slow-growing tumors that cause the pituitary gland to produce excessive amounts of growth hormone, leading to the characteristic symptoms of acromegaly such as enlargement of the bones and soft tissues.
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Features of hypoglycaemia do not include:
- A. Drenching sweat
- B. Tachycardia
- C. Tachypnoea
- D. Brisk jerk
Correct Answer: D
Rationale: Hypoglycemia is characterized by a low blood sugar level, which can lead to various symptoms. The features of hypoglycemia typically include drenching sweat, tachycardia (increased heart rate), and tachypnea (rapid breathing). A brisk jerk, on the other hand, is not a typical feature of hypoglycemia. Symptoms such as confusion, dizziness, shakiness, hunger, weakness, and irritability are more commonly associated with hypoglycemia than a brisk jerk.
Thyroid-stimulating hormone (TSH):
- A. is synthesized in parafollicular cells
- B. is a template for thyroid hormone biosynthesis.
- C. is derived from iodinated tyrosine residues.
- D. secretion is inhibited by TRH from the hypothalamus.
Correct Answer: D
Rationale: Thyroid-stimulating hormone (TSH) is a hormone produced by the anterior pituitary gland. It stimulates the thyroid gland to produce and release thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3). TSH secretion is regulated by the hypothalamus via the release of thyrotropin-releasing hormone (TRH). TRH acts on the anterior pituitary gland to stimulate the production and release of TSH. Therefore, TSH secretion is indeed inhibited by TRH, not stimulated as in the other options.
Which of the following statements best describes Cushing's syndrome?
- A. Cushing's syndrome refers to a disease process caused by abnormally high levels of cortisol
- B. Cushing's syndrome refers to a disease process caused by abnormally low levels of aldosterone
- C. Cushing's syndrome refers to a disease process caused by abnormally high levels of aldosterone
- D. Cushing's syndrome refers to a disease process caused by abnormally low levels of cortisol
Correct Answer: A
Rationale: Cushing's syndrome is a condition characterized by excessive levels of cortisol in the body. Cortisol is a hormone produced by the adrenal glands that helps regulate various bodily functions, including metabolism, immune response, and stress response. When there is an overproduction of cortisol, either due to excessive production by the adrenal glands or prolonged use of corticosteroid medications, it can result in Cushing's syndrome. Symptoms of Cushing's syndrome include weight gain, particularly in the face and abdomen, high blood pressure, muscle weakness, and irregularities in menstruation. It is important to diagnose and manage Cushing's syndrome to prevent potential complications such as diabetes, osteoporosis, and cardiovascular disease.
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.
All of the following represent examples of hypothalamic-pituitary negative feedback except:
- A. Cortisol on the CRH-ACTH axis
- B. Gonadal steroids on the GnRH-LH/FSH axis
- C. IGF-1 on the growth hormone-releasing hormone (GHRH)-GH axis
- D. Renin-angiotensin-aldosterone axis
Correct Answer: D
Rationale: The renin-angiotensin-aldosterone axis does not involve the hypothalamus or pituitary gland; instead, it primarily involves the kidneys and the renin-secreting cells. In this axis, renin is released in response to low blood pressure, leading to the formation of angiotensin II and the subsequent release of aldosterone from the adrenal glands. Feedback mechanisms for this axis primarily involve the regulation of renin release based on blood pressure rather than involving direct negative feedback from downstream hormones on the hypothalamus or pituitary gland. On the other hand, choices A, B, and C all involve classic examples of hypothalamic-pituitary negative feedback loops where the end hormone suppresses the release of the stimulating hormones at the hypothalamic and pituitary levels.