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Parathyroid function in relation to intestinal function and renal calcium reabsorption in patients with
M Lindsjö1, B G Danielson, B Fellström
1Department of Internal Medicine, University Hospital, Uppsala, Sweden.
Scandinavian Journal of Urology and Nephrology
|January 1, 1992
Summary
In recurrent kidney stone formers, high urinary calcium is often due to intestinal hyperabsorption, not high parathyroid hormone (PTH). Intestinal issues and impaired kidney calcium handling were equally common causes of elevated PTH.
Area of Science:
- Nephrology
- Endocrinology
- Metabolic Bone Disease
Background:
- A new method for measuring intact parathyroid hormone (PTH) allows for better assessment of parathyroid function.
- Recurrent renal stone formation is a common condition with complex underlying causes.
Purpose of the Study:
- To evaluate parathyroid function in recurrent renal stone formers using intact PTH measurements.
- To investigate the roles of intestinal calcium absorption and renal calcium handling in hypercalciuria and elevated PTH.
Main Methods:
- Measured intact PTH, serum calcium, urinary calcium, and urinary oxalate in 324 recurrent renal stone formers.
- Conducted oral calcium loading tests and analyzed electrolytes in patients with elevated PTH to differentiate renal and intestinal factors.
Main Results:
- Intact PTH was inversely related to urinary and serum calcium, suggesting intestinal hyperabsorption as a primary cause of hypercalciuria.
- Elevated serum PTH (7% of patients) was associated with either intestinal malfunction or impaired renal calcium conservation.
- Intestinal malfunction led to reduced calcium absorption and enhanced tubular reabsorption of calcium (TRCa), while renal issues showed inappropriately low TRCa during calcium load.
Conclusions:
- Hypercalciuria in many recurrent stone formers is driven by intestinal calcium hyperabsorption rather than elevated PTH.
- Both intestinal dysfunction and impaired renal calcium handling contribute to elevated PTH in stone formers, often without overt symptoms.
- The study highlights the importance of assessing both intestinal and renal factors in managing recurrent renal stone disease.