Plasma somatostatin activity in medullary cancer of the thyroid.

In a group consisting of 50 adults and 5 children with diagnosed or suspected medullary cancer of the thyroid, plasma somatostatin levels were measured in 77 samples with a sensitive radioimmunoassay. Only 2 patients had clearly enhanced plasma somatostatin immunoreactivity, both with highly active aggressive tumors. Other patients had plasma somatostatin levels of under 20 ng/l or undetectable ones. No evidence of response of somatostatin levels to pentagastrin stimulation was found.