In the pancreas, which are the cells that secrete insulin, decrease the blood levels of glucose.

Correct Answer: C

Rationale: Beta cells in pancreatic islets secrete insulin, lowering blood glucose by driving cellular uptake and glycogen storage. Delta cells release somatostatin, inhibiting other hormones. Alpha cells produce glucagon, raising glucose. 'Gamma' isn't a pancreatic cell type possibly a typo (Q4 lists 'beta' twice). Beta cells' insulin role distinguishes them, critical for glucose homeostasis, unlike inhibitory or glucose-elevating cells.

Correct Answer: B

Rationale: Calcitonin, from thyroid C-cells, lowers blood calcium by bone deposition, countering PTH. Adrenal cortex produces steroids (e.g., cortisol), not calcitonin. Pituitary regulates via TSH, not secreting calcitonin. Thymus releases thymosin for immunity. Thyroid's calcitonin role distinguishes it, key to calcium balance, unlike adrenal, pituitary, or immune glands.

Correct Answer: A

Rationale: Steroids, lipid-soluble, diffuse across membranes, enter nuclei, and activate genes for protein synthesis (e.g., cortisol effects). They don't catalyze cAMP peptide hormones do via membrane receptors and G-proteins. This limitation distinguishes steroid mechanisms, key to genomic actions, contrasting with second-messenger systems.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.