Question

The blood calcium is lowered in deficiency of
A. Calcitonin
B. Both calcitonin and parathormone
C. Thyroxine
D. Parathormone

Answer 1

Hint: Parathyroid gland is a very crucial endocrine gland which is present in close proximity to the thyroid gland and has its importance in producing the hormone that maintains the calcium levels in blood. The chief cells of the gland produce the hormone. The hormone is very essential in maintaining a healthy life.

Complete answer:
Calcium is very crucial for many functions in the body like -
1. To maintain strong bones
2. Muscle contraction
3. Nerve conduction
4. Blood clotting
It is very important to maintain blood calcium levels. The endocrine gland, a parathyroid which is located close to the thyroid, is responsible for making the hormone which helps in increasing calcium levels in blood, which is a parathormone. It influences bone resorption. It is secreted in situation of low blood calcium levels. It stimulates osteoclast activity in the bone to release more calcium (Ca²⁺) into the blood to increase a low calcium level. The bones act as a reservoir of calcium. The causes of low levels may be of metabolism, stress, and nutritional variations or an increase of calcitonin which increases calcium absorption from blood. Parathormone is secreted by the chief cells of the parathyroid glands.
Thyroxine hormone increases the basal metabolic rate.
Calcitonin is a  peptide hormone secreted by parafollicular cells or C cells of the thyroid gland, It reduces blood calcium, have opposite effect of parathyroid hormone. It maintain calcium homeostasis by inhibiting osteoclast activity when calcium levels in blood are raised. It also inhibits reabsorption of Ca²⁺ and phosphate in renal tubules, allowing them to be excreted.
Decreased blood calcium levels lead to hypocalcemia.

So, the correct answer is “Option D”.

Note:
An increased calcitonin level can also cause hypocalcemia which is a dreadful situation in which muscle contractility is decreased, nerve conduction is decreased, blood clotting is impaired and has drastic lethal effects on the heart too. People with low calcium levels are more prone to bone fracture.