MCAT® ExamBiological and Biochemical Foundations of Living SystemsEasy
A patient presents with symptoms including muscle weakness, cramps, and irregular heart rhythms. Blood tests reveal abnormally low levels of calcium. Which endocrine gland is most likely malfunctioning in this patient?
- APancreas
- BParathyroid glands
- CThyroid gland
- DAdrenal gland
Show answer & explanationAnswer & explanation
Correct answer: B. Parathyroid glands
The parathyroid glands are responsible for producing parathyroid hormone (PTH), which plays a critical role in regulating calcium levels in the blood. Low calcium levels (hypocalcemia) are a direct consequence of insufficient PTH, often due to parathyroid gland malfunction.
Why the other options are wrong
- A. The pancreas regulates blood glucose levels through insulin and glucagon, not calcium.
- C. The thyroid gland primarily regulates metabolism and produces calcitonin, which lowers blood calcium, but parathyroid hormone is the main regulator for increasing calcium.
- D. The adrenal glands produce hormones like cortisol and adrenaline, involved in stress response and metabolism, not primary 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 blood calcium and phosphate levels, increasing calcium by stimulating bone resorption, kidney reabsorption, and vitamin D activation.
- Produces parathyroid hormone (PTH).
- PTH increases blood calcium levels.
- Acts on bones, kidneys, and intestines (via vitamin D).
- Essential for nerve and muscle function.
Memory trick: PTH: 'Pulls' That 'Hard' Calcium from bones.