Pituitary TSH in normal subjects and in patients with asymptomatic atrophic thyroiditis: Evidence for its...

Biological and radioimmunological measurements of pituitary TSH concentration were performed in 22 cases of asymptomatic atrophic thyroiditis and in 18 controls. Whilst bioassay revealed the presence of a greater pituitary TSH concentration in thyroiditis cases, radioimmunoassay failed to confirm such a difference. The reason therefore seems to lie in the presence in thyroiditis pituitatries of a TSH which reacted in the bioassay but showed only a weak affinity for the anti-hTSH antiserum. The slopes of radioimmunological dilution curves of the pituitary extracts were indeed significantly lower with thyroiditis pituitaries than with controls. When the whole population sample was considered, a negative correlation existed between the ratio of biological and radioimmunological TSH determinations (B/I) and the slope of the corresponding dilution curves. Since in radioimmunoassay a low displacement slope is indicative of a weak immunological affinity of the antigen for the antiserum, this demonstrated negative correlation suggests together with a high B/I ratio, even in normal people.