Biology · Chemical Coordination and Integration · NEET
Osteoporosis is an age-related disease of the skeletal system in which bone mass and bone strength decrease, so bones become weak and break easily. The main cause in NEET is a decreased level of estrogen, which happens in aged women after menopause. Two hormones are linked to it: estrogen (its fall causes bone loss) and parathyroid hormone or PTH (it removes calcium from bone). Memory hook: "Old age + low Estrogen = weak bones."
Low estrogen (after menopause) and PTH-driven bone resorption make bone breakdown exceed bone building, lowering bone mass and causing osteoporosis.
Your doubts, answered
Is osteoporosis caused by low estrogen or by low calcium?
For NEET the answer is decreased estrogen. In the 2016 PYQ the correct option is 'Decreased level of estrogen', not high or low calcium. When estrogen falls after menopause, bone breakdown becomes faster than bone building, so bone mass drops. Low blood calcium is not the direct NCERT cause of osteoporosis.
Which two hormones does NEET link with osteoporosis?
Estrogen and Parathyroid hormone (PTH). This is the exact answer to the 2018 PYQ. A fall in estrogen after menopause promotes bone loss, while PTH acts on bone to cause bone resorption (removing calcium from bone). Both affect bone and calcium, so both are tied to osteoporosis.
Is osteoporosis an autoimmune disorder?
No. In the 2019 PYQ, the autoimmune disorder is Myasthenia gravis, not osteoporosis. Osteoporosis is simply an age-related decrease in bone mass. Arthritis is inflammation of joints and gout is caused by uric acid crystals, so none of these three are autoimmune either.
How does PTH lead to weaker bones?
PTH is a hypercalcemic hormone. It stimulates bone resorption, which means it dissolves bone and releases calcium into the blood to raise blood Ca2+ levels. If this bone resorption continues too much, the bone loses mineral and becomes weak, which links PTH to osteoporosis.
Why does osteoporosis happen mostly in aged women?
After menopause the ovary produces much less estrogen. Estrogen normally protects the skeleton and keeps bone building strong. When estrogen drops, bone breakdown wins over bone formation, so bone mass falls. This is why the NCERT calls osteoporosis an age-related disease common in older women.
⚠️ The NEET trap ✗ Osteoporosis is caused by a high concentration of Ca2+ and Na+ ions in the blood. ✓ Osteoporosis is caused by a decreased level of estrogen (age-related, common after menopause). The hormones involved are estrogen and PTH. 🧠 NTA hides calcium options to trick you. The cause is LOW estrogen, not any calcium level. Calcium moves out of bone, but the cause you must pick is low estrogen.
Real NEET questions
NEET 2016
Osteoporosis, an age-related disease of skeletal system, may occur due to
A · Immune disorder affecting neuromuscular junction leading to fatigue
B · High concentration of Ca++ and Na+
C · Decreased level of estrogen ✓
D · Accumulation of uric acid leading to inflammation of joints
Solution: Osteoporosis (loss of bone mass) commonly occurs in aged women after menopause due to a fall in estrogen. Estrogen helps maintain bone integrity, so its decline weakens the skeleton. Option A describes Myasthenia gravis and option D describes gout.
NEET 2018
Which of the following hormones can play a significant role in osteoporosis?
A · Estrogen and Parathyroid hormone ✓
B · Progesterone and Aldosterone
C · Aldosterone and Prolactin
D · Parathyroid hormone and Prolactin
Solution: Both estrogen and parathyroid hormone (PTH) affect bone and calcium balance. PTH stimulates bone resorption (demineralisation) and raises blood Ca2+, while a fall in estrogen after menopause promotes bone loss, tying both hormones to osteoporosis.
NEET 2019
Which of the following diseases is an autoimmune disorder?
A · Myasthenia gravis ✓
B · Arthritis
C · Osteoporosis
D · Gout
Solution: Myasthenia gravis is an autoimmune disorder affecting the neuromuscular junction. Osteoporosis is an age-related decrease in bone mass, arthritis is joint inflammation and gout is due to uric acid crystals, so none of these three is autoimmune.
Solved Chemical Coordination and Integration NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
What is the single most common cause of osteoporosis for NEET?
Decreased level of estrogen. This is the direct answer NCERT and NEET expect. It usually happens in aged women after menopause when the ovary makes less estrogen.
Which hormones are involved in osteoporosis?
Estrogen and Parathyroid hormone (PTH). Estrogen loss causes bone loss, and PTH causes bone resorption that removes calcium from bone.
Is calcitonin (TCT) involved in osteoporosis?
Calcitonin lowers blood calcium and protects bone by reducing bone loss, but the NEET answer for the cause of osteoporosis is low estrogen. TCT is more about calcium regulation than the direct cause asked in exams.
What type of disease is osteoporosis?
It is an age-related disease of the skeletal system with reduced bone mass and strength. It is NOT autoimmune, NOT joint inflammation (arthritis), and NOT caused by uric acid (gout).
Does PTH cause or cure osteoporosis?
PTH stimulates bone resorption, which removes calcium from bone. Too much bone resorption weakens bone, so PTH is one of the hormones linked to osteoporosis in NEET questions.
