Question

A tumour in an endocrine gland caused Jennifer to have weakened bones and unusually high levels of blood calcium. Which of the following was affected?
A) Anterior pituitary
B) Pancreas
C) Adrenal glands
D) Parathyroid glands

Answer 1

Hint: These are four small glands present on the backside of the thyroid gland, one pair each in two lobes of the thyroid gland. It secretes collip’s hormone or parathyroid hormone that increases levels of calcium in the blood.

Complete step-by-step answer:
Secretion of parathyroid hormone by the parathyroid gland is regulated by the calcium level in blood and not by hypothalamic or pituitary hormones. Bone tissue acts as a storage reservoir for calcium and PTH stimulates the removal of calcium from the bone to increase levels in the blood; therefore it stimulates osteoclastic activity.
It increases the reabsorption of calcium by the renal tubules of the kidney so that less is lost in urine but at the same time it stimulates the loss of phosphates in the urine. It also stimulates the kidney to secrete calcitriol which in turn, increases calcium absorption from the digested food in the gut. PTH is thus a hypercalcemic hormone i.e., it increases the blood calcium levels.
If the bones are weakened that means calcium is released from bones and this is done by parathyroid glands.
Hence the correct answer is option d.

Note: Calcitonin is a peptide hormone secreted by parafollicular cells of the thyroid gland that are distinct from the thyroid follicles. Thyroid cells produce calcitonin in response to high calcium levels in the blood. It decreases plasma calcium concentration by decreasing the mobilisation of calcium from bones; therefore promoting osteoblastic activity.