Castration of mice at 50 and 100 days of age (early adult and late adult castration series) is followed by typical histological changes in the thyroid glands, and the histometrical measurements make it possible to divide their sequential changes into three stages.
The first stage lasting about 30 days (in the early adult castration series) or 40 days (in the late series) after castration is characterized by the abrupt increase of large follicles exceeding 50μ in diameter, in frequency per mm
2, static maintenance of their maximum level and their rapid decrease to the normal range concomitantly, a similar sequence of dark colloid is observed. This is evidently interpreted as showing rapid accumulation, static storage and abrupt release of much colloid.
The second stage after the previous stage to until about the 120th postoperative day, is marked by the continued maintenance of almost the same level in frequency as the normal for the large follicles, fluctuations in staining of colloid and cell activation of considerable degrees. The thyroid pattern in the castrates, especially in the early adult castrates, resembles that of the corresponding normal controls.
The third stage represents a trend toward colloid accumulation indicated by the occurrence of dark colloid, general decrease in cell height of follicle cells, further increase in frequency within the normal range of the large follicles and frequent occurrence of enormously grown follicles.
Concerning the degrees of these changes, there is apparently a time element related to the age at castration. In the late adult castration series, the change in the first stage greater in degree, that in the second smaller and that in the third greater again, while in the early series they are reversed.
No sex difference is found in the histological changes in the thyroid glands of both castration series.
Still another point of interest is that secretory droplets appear often in both castration series, but rare in the normal control series.
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