Mast cell hyperplasia during goitrogen-induced thyroid growth - a quantitative study.

This paper describes the effect of long-term goitrogen-administration on the mast cell population of the rat thyroid. Animals were treated with the goitrogen aminotriazole at a dose sufficient to block thyroid hormone synthesis completely, and compared after 80 days with a control group. Serum TSH was measured by radioimmunoassay, and mast cell number quantified from specially-stained tissue sections using appropriate serological methods. Goitrogen treatment led to a 9-fold increase in serum TSH and an 8-fold increase in thyroid weight. Mast cell number per unit volume of thyroid decreased, but total numbers per gland increased 4 to 5 fold. There was a significant fall in mean mast cell size. The work demonstrates conclusively that mast cell hyperplasia occurs during goitre formation and provides a method for its quantitative assessment. The possible mechanisms and significance of thyroid mast cell proliferation are discussed.