UPSC Prelims 2007 Q113: Science & Technology – Biology
In the human body
which one of the following hormones regulates blood calcium and phosphate?
- (a) Glucagon
- (b) Growth hormone
- (c) Parathyroid hormone
- (d) Thyroxin
Answer: (c) Parathyroid hormone
Explanation
Calcium and phosphate control — parathyroid hormone (PTH)
| Hormone | Gland | Effect on blood calcium |
|---|---|---|
| Parathyroid hormone (PTH) | Parathyroid | Raises Ca²⁺ — releases bone calcium, increases kidney reabsorption, activates vitamin D; lowers phosphate |
| Calcitonin | Thyroid (C-cells) | Lowers Ca²⁺ |
Other options:
| Hormone | Main job |
|---|---|
| Glucagon | Raises blood sugar (pancreas α-cells) |
| Growth hormone | Growth of bones and tissues (anterior pituitary) |
| Thyroxine | Basal metabolic rate (thyroid) |
Answer: (c) Parathyroid hormone.
Why each option is right or wrong
- (a) Incorrect. Glucagon controls blood glucose, not calcium.
- (b) Incorrect. Growth hormone controls growth.
- (c) CORRECT. PTH regulates blood calcium and phosphate.
- (d) Incorrect. Thyroxine controls metabolic rate.
Key point
PTH raises blood Ca²⁺ and lowers phosphate; calcitonin lowers Ca²⁺. They work as a pair.
Remember
Parathyroid hormone regulates blood calcium and phosphate.
Common mistakes
- Choosing thyroxine because the parathyroids sit on the thyroid gland.
- Forgetting calcitonin — the opposing hormone from the thyroid.
- Mixing up the parathyroid (calcium) with the pancreas (glucose).
Exam tip
PTH = 'Pulls calcium To the Blood'. Calcitonin = 'Calcium Tone-down'.
Sources
- NCERT Class XI — Biology, Ch 19 (Chemical Coordination and Integration)
- NCERT Class X — Science, Ch 6 (Life Processes)