Immunoreactive parathyroid hormone, calcium, and magnesium in human cerebrospinal fluid

Parathyroid hormone (PTH) was measured radioimmunologically in simultaneous plasma and cerebrospinal fluid (CSF) samples obtained from 72 patients aged 20 to 80 years without endocrine or psychiatric diseases and from 2 patients aged 40 and 70 years with secondary hyperparathyroidism due to renal insufficiency. They underwent routine diagnostic lumbar puncture because of suspected prolapse of a disc. Total calcium (Ca) and magnesium (Mg) were also determined in these samples by complexometry . The following findings were obtained (ng/ml, median, range in brackets): Plasma PTH 1.7 (0.7-6.6); CSF PTH 0.8 (0.5-2.3), respectively. No correlation was found between PTH concentrations in plasma and CSF in all 74 samples. The Ca concentrations in plasma, with a median of 2.3 mmol/l (2.1-2.6) were significantly higher than the Ca concentrations in CSF (median 1.1 mmol/l, range 0.4-1.3). The correlation between PTH and calcium levels in CSF was only weak (r = 0.284 P less than 0.05). The Mg levels in CSF (median 1.1 mmol/l, range 0.7-1.6) were higher than Mg concentrations in plasma (median 0.9 mmol/l, range 0.6-1.1). No correlation was found between PTH and Mg in CSF. Our study demonstrated that in man PTH is a normal constituent of CSF.