Parathyroid glands also have a connective tissue capsule that extends septa into the gland like the patient’s slide exhibits. However, the parathyroid glands consist of densely packed clusters of principal (chief) cells that secrete parathyroid hormone (PTH) in response to decreased blood calcium levels.

PTH binds receptors on osteoblasts. What paracrine factor is secreted by osteoblasts that stimulate osteoclasts?