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

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Abstract
Parathyroid hormone (PTH) was measured radioimmunologically in simultaneous plasma and CSF samples obtained from 72 patients aged 20-80 yr without endocrine or psychiatric diseases, and from 2 patients aged 40 and 70 yr with secondary hyperparathyroidism due to renal insufficiency. They underwent routine diagnostic lumbar puncture because of suspected prolapse of a disc. Total Ca and 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 Ca levels in CSF was only weak (r = 0.284, P < 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. In man PTH apparently is a normal constituent of CSF.