Which of the following statements is incorrect?

• A. Pineal gland secretes melatonin which is essential to maintain circadian rhythm.
• B. Anterior pituitary maintains fluid balance by regulating the adrenal glands.
• C. Pancreas regulates blood sugar levels by secreting or absorbing insulin and glucagon.
• D. Thyroid gland secretes T₃ and T₄ which are critical in the regulation of metabolism.

Answer: (C)

Verified step by step guidance

1. Step 1: Review the function of the pineal gland. It secretes melatonin, which helps regulate the circadian rhythm, the body's internal clock for sleep-wake cycles. This statement is correct.
2. Step 2: Examine the role of the anterior pituitary gland. It secretes hormones that regulate various endocrine glands, but it does not directly maintain fluid balance by regulating the adrenal glands. Instead, fluid balance is primarily controlled by hormones like antidiuretic hormone (ADH) and aldosterone, which involve the posterior pituitary and adrenal cortex respectively.
3. Step 3: Analyze the statement about the pancreas. The pancreas regulates blood sugar levels by secreting insulin and glucagon. However, it does not 'absorb' these hormones; it only secretes them. This makes the statement incorrect because of the mention of absorption.
4. Step 4: Consider the thyroid gland's function. It secretes triiodothyronine (T3) and thyroxine (T4), which are essential for regulating metabolism. This statement is accurate.
5. Step 5: Conclude that the incorrect statement is the one about the pancreas, due to the inaccurate claim that it absorbs insulin and glucagon, which it does not.