Sam was a 60 year old man. As a result of picking up a heavy object he fractured the radius and ulna of his right arm. X-rays indicated that he had severe osteoporosis. His blood calcium levels were above normal and the pathologist found cancer cells that produced a hormone ike substance. That substance was most likely A. vitamin D. B. parathyroid hormone. C. calcitonin. thyroid hormone growth hormone

The parathyroid hormone is secreted by the parathyroid gland and it is responsible for regulating the calcium levels in the serum.
Parathyroid hormone is able to exert its effect on the kidney, intestine and the bone and by exerting its effect on these organs it is able to regulate the calcium levels.
This hormone is secreted when the levels of calcium in the serum are low and this hormone is able to exert its effect by acting on the bones and stimulating the osteoclasts activity which causes the release of calcium from the bones and thus, the serum levels of calcium are elevated again.
If the levels of the parathyroid hormone would increase the reabsorption of calcium from the bone would be more and hence, it would lead to osteoporosis. Thus, it can be concluded that Sam's cancer cells are producing parathyroid hormone.