Vitamin D status and redefining serum parathyroid hormone reference range in the elderly

Area of Science:

• Endocrinology
• Geriatrics
• Nutritional Science

Background:

• Subclinical vitamin D insufficiency is linked to secondary hyperparathyroidism and increased fracture risk.
• Established reference ranges for serum parathyroid hormone (PTH) often do not account for vitamin D status, particularly in the elderly.

Purpose of the Study:

• To investigate the impact of vitamin D status on serum PTH levels in healthy elderly individuals.
• To determine if current PTH reference ranges adequately reflect secondary hyperparathyroidism in the context of low 25-hydroxyvitamin D (25OHD).

Main Methods:

• Measured serum PTH, total calcium, albumin, phosphate, creatinine, bone markers, and 25OHD in 280 healthy subjects (aged 60-79).
• Utilized two different immunoradiometric assays for serum PTH measurement.
• Analyzed PTH concentrations in relation to serum 25OHD levels.

Main Results:

• A high prevalence (59.6%) of low serum 25OHD (< or =30 nmol/L) was observed in the study group.
• PTH concentrations were lower in subjects with adequate 25OHD levels compared to the entire group.
• Approximately 25% of subjects with low 25OHD showed elevated PTH, indicating secondary hyperparathyroidism that could be missed with standard reference ranges.

Conclusions:

• Vitamin D status is a critical factor influencing serum PTH levels in the elderly.
• Current reference values for serum PTH may underestimate secondary hyperparathyroidism in individuals with vitamin D insufficiency.
• Establishing vitamin D-adjusted PTH reference ranges is recommended for accurate assessment in elderly populations.