Explaining Low Vitamin D and Elevated PTH to Parents
Your child's blood tests show low vitamin D levels and elevated parathyroid hormone (PTH), which means their body is not getting enough vitamin D, causing the parathyroid glands to work overtime to maintain normal calcium levels in the blood. 1
What These Results Mean
Understanding Vitamin D Deficiency
Vitamin D is essential for calcium absorption and bone health. When vitamin D levels drop below 30 ng/mL (75 nmol/L), the body cannot absorb calcium properly from food, which can lead to weak bones and poor growth in children 1.
The parathyroid glands respond to low vitamin D by producing more PTH to pull calcium from the bones into the bloodstream to maintain normal blood calcium levels 1. This is called "secondary hyperparathyroidism" and is the body's protective mechanism 1.
Research shows that in children, PTH levels begin to rise when vitamin D drops below approximately 18-34 ng/mL, indicating the body is struggling to maintain calcium balance 2, 3.
Why This Happens in Children
Common reasons for vitamin D deficiency in children include 1:
- Limited sun exposure (vitamin D is made in the skin when exposed to sunlight)
- Insufficient dietary intake of vitamin D-rich foods (fatty fish, egg yolks, fortified milk)
- Darker skin pigmentation (requires more sun exposure to produce the same amount of vitamin D)
- Seasonal variation (winter months with less sunlight)
- Rapid growth periods (increased vitamin D demands)
What Could Happen Without Treatment
Short-term Concerns
- Bone and muscle pain may develop 1
- Muscle weakness can occur 1
- Increased bone resorption (the body breaking down bone to release calcium) 4
Long-term Risks if Untreated
- Rickets (bone softening and deformities) can develop in severe deficiency, particularly when vitamin D levels fall below 34 nmol/L (approximately 14 ng/mL) 2
- Reduced bone mineral density and increased fracture risk 1, 4
- Impaired growth and failure to reach full height potential 4
- Dental problems including delayed tooth eruption and enamel defects 1
The Treatment Plan
Vitamin D Supplementation
Your child will need vitamin D supplementation based on the severity of deficiency 1, 5:
- For severe deficiency (vitamin D <5 ng/mL): Higher therapeutic doses are required for 2-4 months 1
- For mild deficiency (5-15 ng/mL): Moderate therapeutic doses for 2-3 months 1
- For insufficiency (16-30 ng/mL): Lower therapeutic doses for 3 months 1
Maintenance After Correction
- Once vitamin D levels are restored to above 30 ng/mL, daily maintenance supplementation of 200-1,000 IU is recommended to prevent recurrence 1, 5.
Monitoring During Treatment
Blood tests will be needed to ensure safe and effective treatment 1:
- Calcium and phosphorus levels should be checked one month after starting vitamin D supplementation to ensure levels remain normal and avoid over-treatment 1, 5
- Vitamin D levels should be rechecked after completing the initial treatment course 1
- PTH levels should normalize as vitamin D is repleted 1
Important Safety Points
What to Watch For
- Excessive vitamin D can cause high calcium levels (hypercalcemia), though this is rare at recommended doses 1
- Signs of too much calcium include excessive thirst, frequent urination, nausea, or constipation 1
Dietary Support
Encourage vitamin D-rich foods to complement supplementation 1:
- Fatty fish (salmon, mackerel, sardines)
- Egg yolks
- Fortified milk and dairy products
- Fortified cereals
Ensure adequate calcium intake (varies by age: 200-1,150 mg daily depending on age) to support bone health during treatment 1.
Lifestyle Modifications
- Safe sun exposure (10-15 minutes of sunlight on arms and legs several times per week, with appropriate sun protection to avoid burns) can help maintain vitamin D levels 1
- Regular physical activity supports bone health 1
Expected Timeline
- PTH levels typically begin to normalize within 1-3 months of adequate vitamin D supplementation 1
- Complete correction of deficiency usually takes 2-4 months depending on severity 1
- Annual monitoring of vitamin D levels is recommended once levels are stable to ensure they remain adequate 1, 5
Why This Matters for Your Child's Future
Childhood and adolescence are critical periods for bone development, with approximately 90% of peak bone mass achieved by age 18 4. Correcting vitamin D deficiency now ensures your child can build strong bones that will last a lifetime and reduces the risk of osteoporosis in adulthood 1, 4.