Earliest changes observed by ophthalmoscope in background retinopathy of diabetes is:

Correct Answer: B

Rationale: The earliest changes observed by ophthalmoscope in background retinopathy of diabetes is typically the presence of microaneurysms. These are small dilations of retinal capillaries due to weakening of the vessel walls caused by diabetes-induced damage. Microaneurysms are a hallmark sign of diabetic retinopathy and are often the first visible sign on retinal examination. Other changes in diabetic retinopathy, such as venous dilatation, increased capillary permeability, and arteriovenous shunts, may develop later in the disease process as it progresses.

Correct Answer: C

Rationale: Growth hormone deficiency (GHD) is commonly associated with decreased bone mineral density, leading to an increased risk of fractures and osteoporosis. Therefore, increased bone mineral density would not typically be a sign or symptom of GHD. On the other hand, abnormal lipid profile, atherosclerosis, and left ventricular dysfunction are all potential signs or symptoms of GHD. Abnormal lipid profile can manifest as increased levels of LDL cholesterol and decreased levels of HDL cholesterol. Atherosclerosis, the buildup of plaque in the arteries, can occur in individuals with GHD due to the impact on lipid metabolism. Left ventricular dysfunction may also be seen in individuals with GHD due to the role of growth hormone in cardiac function and structure.

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.

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.

Correct Answer: A

Rationale: Hypertonicity (increased osmolarity or high concentration of solutes in the blood) is the most potent stimulus for the hypothalamic production of arginine vasopressin (also known as antidiuretic hormone or ADH). When the body senses increased plasma osmolality, the osmoreceptors in the hypothalamus stimulate the release of vasopressin from the posterior pituitary gland. Vasopressin acts on the kidneys to increase water reabsorption and decrease urine output, helping to restore normal osmolarity. This mechanism helps to conserve water and maintain body fluid balance in response to dehydration or increased solute concentration in the blood.