Thyroid Peroxidase and Thyroglobulin Expression in Normal Human Thyroid Glands.

The objective of the present study was to investigate thyroid peroxidase (TPO) and thyroglobulin (Tg) expression in normal thyroid tissue. Thirty-eight normal thyroids from fetuses(1) children, adults, and elderly subjects were evaluated. TPO and Tg expression was determined by analyzing at least 200 cells/specimen. A value of 80% was considered to be the threshold for TPO positivity. In terms of age, TPO expression occurs in fetuses along with follicle differentiation and is absent in solid follicles. TPO staining was cytoplasmic, and was more intense in the apical membrane in tissue from fetuses, children, and young adults. A perinuclear rang was found in tissue from older adults and from the elderly subjects. There was concomitant TPO and Tg expression in all groups studied. Tg expression was observed in all normal thyroids from all age groups. Tg expression was extremely variable (10-100% of the cells) and fainter than TPO expression.