The process of development of thyroidectomy cells from the so-called thyrotrophs.

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Abstract
The process of development of thyroidectomy (TX) cells from the so-called thyrotrophs (the H-type cells by Yoshimura et al., 1977) was electron-microscopically investigated at intervals of 12 hr, 1, 3, 5, 7 and 14 days after TX. Cytological changes of the II-type cells vary from cell to cell even at the same intervals after TX. From 12 hr to 5 days, the II-type cells are characterized by the deprivation of secretory granules and the enlargement of cell size. When extensively degranulated, the II-type cells appear as vesiculated cells with a round or oval shape, resembling the LH-gonadotrophs (the III-type cells). The frequent detection of III- and IV-type cells (FSH-gonadotrophs) is in striking contrast with the infrequent detection of IItype cells within 12 hr and 1 day. Some pre-existed IV-type cells show retrogressive signs after TX. Some other IV-type cells are moderately granulated, at 1, 3 and 5 days, followed by the deprivation of the stored secretory granules, resulting in the vesiculated cells. These cells begin to appear at 3 days and increase in number at 5 and 7 days, despite the individual disparity in development. They may be the immature TX-cells characterized by the closure of Golgi lamellae, and by granules of low density in the small, irregularly shaped cisternae. They gradually increase in dimensions with the lapse of time. Degranulation and accumulation of large cisternae with progressive sedimentation of intracisternal granules may account for the maturation of TX-cells. By 14 days the maximal diameter of the mature TX-cells becomes 3-4 times as large as that of an acidophil. From the present observations, it is tentatively concluded that TX cells may not directly develop from the II-type cells, but indirectly through the III- or IV-type cells; and that the TX-cells may not be hyperfunctioning thyrotrophs, but rather dysfunctioning basophils.