Question

osteoblasts are stimulated by: a parathyroid hormone b calcitonin c adrenocorticotropic hormone d thyroid stimulating hormone

Explanation:

• Option A: Parathyroid Hormone (PTH) mainly acts on osteoclasts to increase bone resorption, not stimulate osteoblasts directly in the main action.
• Option B: Calcitonin is produced by the thyroid gland. It inhibits osteoclast activity and stimulates osteoblasts to promote bone formation (depositing calcium into bones), which matches the requirement of stimulating osteoblasts.
• Option C: Adrenocorticotropic Hormone (ACTH) is related to the adrenal cortex and the stress response, with no direct role in stimulating osteoblasts.
• Option D: Thyroid Stimulating Hormone (TSH) acts on the thyroid gland to regulate thyroid hormone production, not osteoblasts.

Answer:

B. Calcitonin