Black thyroid. Morphological, biochemical and geriatric studies on the brown granules in the thyroid follicular cells.

An autopsy case of a 73-year-old man with "black thyroid" was reported. Investigations by light and electron microscopy and histochemical study of the black thyroid material disclosed the massive deposition brown granules in the follicular cells, to be residual bodies containing lipids. Lipids in these granules were mainly composed of phospholipid by biochemical analysis. Concerning the thyroidal function of this case the value of T4-I in the serum was within normal range (4.8-7.5 micrograms/dl) and peroxidase, NADPH-cytochrome C reductase and acid phosphatase activity in the black thyroid material revealed no significant increase or decrease, compared with other 12 autopsied cases. These granules resembled so-called lipofuscin granules, and the frequency and grade of the deposition in autopsied cases increase with aging.