1. We investigated the usefulness of neuropeptide Y as a plasma marker for phaeochromocytoma, ganglioneuroblastoma and neuroblastoma using a simple and highly sensitive r.i.a. for human neuropeptide Y.
2. Plasma immunoreactive neuropeptide Y concentrations were measured without extraction in plasma samples (100 μl) from patients with various diseases.
3. The plasma immunoreactive neuropeptide Y concentration in patients with phaeochromocytoma (172.3 ± 132.4 pmol/l, mean ± sd, n = 23) was significantly higher than that in healthy adult subjects (40.1 ± 10.1 pmol/l, n = 40, P<0.0001). The plasma immunoreactive neuropeptide Y concentrations in patients with ganglioneuroblastoma (590.7 ± 563.6 pmol/l, n = 6) and patients with neuroblastoma (566.9 ± 524.4 pmol/l, n = 15) were significantly higher than those in control children (1–9 years old, 82.2 ± 39.9 pmol/l, n = 72, P<0.0001).
4. The plasma immunoreactive neuropeptide Y concentration in patients with essential hypertension (34.0 ± 3.7 pmol/l, n = 18) was within the normal range, but in patients with chronic renal failure undergoing maintenance haemodialysis (192.1 ± 68.0 pmol/l, n = 25) and in non-dialysed patients with chronic renal failure (85.1 ± 23.1 pmol/l, n = 7) it was significantly higher than that in healthy adult subjects (P<0.0001).
5. Eighty-seven per cent of the patients with phaeochromocytoma, 67% of the patients with ganglioneuroblastoma and 80% of the patients with neuroblastoma showed plasma immunoreactive neuropeptide Y concentrations higher than the upper limits in the control subjects [62 pmol/l (adult) and 160 pmol/l (children)].
6. These results suggest that neuropeptide Y is a useful plasma marker for these tumours in addition to other factors unless the patients have renal failure.