In human physiology, Thyroid and Parathyroid glands play vital roles in regulating metabolism and calcium balance. Although located close to each other in the neck region, they are functionally and structurally different. Questions from this topic frequently appear in NCERT-based exams like UPSC Prelims, SSC CGL, RRB NTPC, CDS, and State PSCs.
This blog post breaks down the differences in a clear, concise, and exam-friendly format using mnemonics, diagrams, and practice questions for better retention and revision.
Difference Between Thyroid and Parathyroid Glands
Definition & Location
◾ Thyroid Gland
🔹 A butterfly-shaped gland located in front of the trachea (windpipe)
🔹 Larger and visible in imaging
◾ Parathyroid Glands
🔹 Four small glands (about the size of a grain of rice)
🔹 Located on the posterior (back) surface of the thyroid gland
Hormones Secreted
◾ Thyroid Gland
🔺 Thyroxine (T4)
🔺 Triiodothyronine (T3)
🔺 Calcitonin
◾ Parathyroid Glands
🔺 Parathyroid Hormone (PTH) only
Function
◾ Thyroid
🔹 Regulates metabolism, growth, and development
🔹 Controls body temperature, energy levels, heart rate
◾ Parathyroid
🔹 Regulates blood calcium and phosphate levels
🔹 Ensures proper nerve and muscle function
Disorders
◾ Thyroid Disorders
🔺 Hypothyroidism – Less thyroxine (e.g., weight gain, fatigue)
🔺 Hyperthyroidism – Excess thyroxine (e.g., weight loss, rapid heartbeat)
🔺 Goitre – Enlargement of the thyroid due to iodine deficiency
◾ Parathyroid Disorders
🔺 Hypoparathyroidism – Low PTH → muscle cramps, spasms
🔺 Hyperparathyroidism – Excess PTH → weak bones, kidney stones
Table: Key Differences Between Thyroid and Parathyroid
| Feature | Thyroid Gland | Parathyroid Glands |
|---|---|---|
| Location | In front of the neck, below the larynx | Embedded behind the thyroid gland (posterior side) |
| Number of Glands | Single gland with two lobes | Four small glands (can vary from 2 to 6) |
| Shape | Butterfly-shaped | Small, oval or bean-shaped |
| Hormones Secreted | Thyroxine (T4), Triiodothyronine (T3), Calcitonin | Parathyroid Hormone (PTH) |
| Main Function | Regulates metabolism, growth, and development | Regulates calcium and phosphate levels in blood |
| Calcitonin Role | Lowers blood calcium levels | — |
| PTH Role | — | Increases blood calcium levels |
| Stimulus for Hormone Release | TSH (Thyroid Stimulating Hormone) from the pituitary | Low calcium levels in the blood |
| Impact on Bones | Indirect (via calcitonin, reduces bone resorption) | Increases bone resorption to release calcium |
| Disorders Related | Hypothyroidism, Hyperthyroidism, Goitre | Hypoparathyroidism, Hyperparathyroidism |
| Developmental Origin | Derived from endodermal tissue of the pharynx | Derived from the third and fourth pharyngeal pouches |
| Feedback Mechanism | Negative feedback via TSH | Negative feedback via calcium levels |
| Relation with Iodine | Requires iodine to synthesize hormones | Does not require iodine |
| Visible Enlargement | Enlargement leads to goitre, visible on neck | Usually not visible externally |
Real-World Analogy
Think of the Thyroid as your body’s thermostat – regulating the speed at which everything runs.
The Parathyroid is like a calcium bank manager, maintaining just the right calcium balance for daily operations.
Quick Revision Notes: Thyroid vs Parathyroid
- Thyroid → T3, T4, Calcitonin → Metabolism
- Parathyroid → PTH → Calcium balance
- Thyroid = big butterfly; Parathyroids = 4 tiny peas
- Iodine is essential only for Thyroid hormones
Practice Questions (MCQs)
Q1. Which hormone is secreted by the parathyroid gland?
A. T3
B. Calcitonin
C. PTH
D. Insulin
✔️ Answer: C. PTH
Q2. The main function of the thyroid gland is:
A. Regulating blood sugar
B. Regulating calcium balance
C. Regulating metabolism
D. Oxygen transport
✔️ Answer: C. Regulating metabolism
Q3. Iodine deficiency affects the production of:
A. Parathyroid hormone
B. Growth hormone
C. Thyroxine
D. Insulin
✔️ Answer: C. Thyroxine
Q4. Hyperparathyroidism can lead to:
A. Anemia
B. Kidney stones
C. Low calcium in blood
D. Fever
✔️ Answer: B. Kidney stones
Q5. Which of the following glands control body temperature and growth?
A. Adrenal
B. Parathyroid
C. Thyroid
D. Pituitary
✔️ Answer: C. Thyroid
Final Takeaway
Though closely located, the thyroid and parathyroid glands have completely different functions. Thyroid hormones control your body’s metabolic rate, while parathyroid hormone (PTH) regulates calcium levels. Understanding these differences is key for both your science fundamentals and for scoring better in competitive exams.
