Your Calcium Thermostat
PTH is the thermostat for blood calcium. When calcium dips even slightly, your parathyroid glands release PTH, which does three things: pulls calcium from bones, tells kidneys to keep calcium and dump phosphorus, and activates vitamin D to absorb more calcium from food. It's a beautifully precise system—unless the thermostat breaks.
What is PTH (Parathyroid Hormone)?
PTH is an 84-amino-acid peptide from the four parathyroid glands. It's the primary regulator of calcium homeostasis. PTH raises calcium by: (1) mobilizing bone calcium, (2) increasing renal calcium reabsorption, (3) stimulating renal 1,25(OH)2D production. Always interpret PTH alongside calcium and vitamin D.
↑ What High PTH (Parathyroid Hormone) Means
Your parathyroid glands are releasing too much PTH. Either they're responding correctly to low calcium/vitamin D (secondary hyperparathyroidism) or they have a tumor making PTH autonomously (primary hyperparathyroidism). The #1 cause of high calcium is primary hyperparathyroidism.
Common symptoms:
Often asymptomatic early · Kidney stones · Bone pain and osteoporosis · Fatigue · Confusion · Constipation · Excessive thirst
↓ What Low PTH (Parathyroid Hormone) Means
Parathyroid glands aren't making enough PTH. Usually from surgical damage (thyroid surgery can accidentally damage parathyroids) or autoimmune destruction. Without PTH, calcium drops dangerously.
Common symptoms:
Muscle cramps and spasms · Numbness and tingling · Seizures (severe) · Dry skin and brittle nails · Dental abnormalities
Why It Matters
When normal:
Maintains blood calcium in tight range
Activates vitamin D in kidneys
Regulates calcium-phosphorus balance
Supports bone remodeling
Risks if abnormal:
High + high calcium = primary hyperparathyroidism (tumor)
High + low/normal calcium = secondary (vitamin D deficiency or kidney disease)
Low: hypoparathyroidism—dangerous hypocalcemia
Chronic PTH elevation = osteoporosis (bone constantly raided)
What Can Cause Abnormal Levels?
Vitamin D Deficiency (high PTH, normal/low calcium)
55% likelyWithout vitamin D, calcium absorption drops. PTH rises to compensate by raiding bones. This is the most common cause of elevated PTH.
Primary Hyperparathyroidism (high PTH, high calcium)
35% likelyA benign parathyroid adenoma produces PTH autonomously, ignoring calcium feedback. Causes high calcium + high PTH.
Chronic Kidney Disease (high PTH)
Kidneys can't activate vitamin D or excrete phosphorus. Rising phosphorus suppresses calcium, driving PTH up.
Surgical Damage (low PTH)
Thyroid/parathyroid surgery can damage or remove parathyroid glands.
Low Calcium Intake
Chronically inadequate calcium intake drives compensatory PTH elevation.
What You Can Do
Optimize vitamin D: 40-60 ng/mL (most common cause of elevated PTH)
Impact: Correcting vitamin D allows calcium absorption and PTH normalization \u00B7 Timeline: 8-12 weeks
Adequate calcium intake: 1000-1200mg daily from food
Impact: Reduces PTH drive to raid bones \u00B7 Timeline: 4-8 weeks
If lifestyle changes aren't enough:
Magnesium optimization (needed for PTH secretion and vitamin D activation)
Impact: Severe Mg deficiency impairs PTH release paradoxically \u00B7 Timeline: 4-8 weeks
If primary hyperparathyroidism: monitor calcium, bone density, kidney stones
Impact: Determines if surgery is needed \u00B7 Timeline: Ongoing
Recommended retest: 3-6 months; sooner if treatment change
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