Question

The blood calcium level is lowered by the deficiency of
(A) Parathormone
(B) Thyroxine
(C) Calcitonin
(D) Both calcitonin and parathormone

Answer 1

Hint: The hormone whose deficiency leads to lowered blood calcium level in blood is secreted by the chief cells of the parathyroid gland which is located in close association with the thyroid gland. A parathyroid gland is a group of four small glands.

Complete step by step answer:
The blood calcium level is lowered by the deficiency of hormone Parathormone. It is also known as the Parathyroid hormone. The parathyroid is an endocrine gland. It regulates the serum calcium ion concentration through its effects on bone, kidney, and intestine.

So, the correct answer is ‘Parathormone’.

Additional Information: Endocrine glands are ductless glands that secrete their hormones directly into the blood. Similarly, the parathyroid gland secretes it’s the hormone directly into the blood. This parathyroid hormone is secreted by the chief cells of the parathyroid glands. It's a polypeptide containing 84 amino acids, which is known to be prohormone. Its molecular mass is something around 9500 Da. Its action is opposed by the hormone calcitonin. Calcitonin is a hormone produced by C-cells of the thyroid gland. Calcitonin works when there is a high concentration of calcium present in the blood. It helps in decreasing blood calcium levels to make it stable in the normal range.

Note: Hyperparathyroidism, the presence of excessive amounts of parathormone within the blood, occurs in two very distinct sets of circumstances. Primary hyperparathyroidism is because of autonomous, abnormal hypersecretion of PTH from the parathyroid, while secondary hyperparathyroidism is an appropriately high PTH level seen as a physiological response to hypocalcemia.