MCAT® ExamBiological and Biochemical Foundations of Living SystemsMedium
A patient presents with symptoms including muscle weakness, cramps, and an irregular heart rhythm. Blood tests reveal significantly low levels of calcium. Which endocrine gland is most likely malfunctioning, leading to these symptoms?
- APancreas
- BThyroid gland
- CParathyroid gland
- DAdrenal gland
Show answer & explanationAnswer & explanation
Correct answer: C. Parathyroid gland
The parathyroid glands are primarily responsible for regulating calcium levels in the blood. They secrete parathyroid hormone (PTH), which increases blood calcium by stimulating osteoclast activity, reabsorption of calcium in the kidneys, and absorption of calcium in the intestines. Low blood calcium (hypocalcemia) directly points to a dysfunction in the parathyroid glands' ability to produce sufficient PTH.
Why the other options are wrong
- A. The pancreas primarily regulates blood glucose through insulin and glucagon, not calcium.
- B. The thyroid gland primarily regulates metabolism and produces calcitonin, which lowers blood calcium, but its primary role isn't elevating calcium.
- D. The adrenal glands produce hormones like cortisol and adrenaline, involved in stress response and metabolism, not calcium regulation.
Parathyroid Gland Function
The parathyroid glands are four small glands located behind the thyroid gland that produce parathyroid hormone (PTH). PTH is the primary regulator of calcium and phosphate homeostasis in the blood.
- Produce parathyroid hormone (PTH)
- Increase blood calcium levels
- Target bones, kidneys, and indirectly intestines
- Essential for nerve and muscle function
Memory trick: Para-Thyroid Pushes The Calcium Up.