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Folia Morphol (Warsz). 2018 Aug 14. doi: 10.5603/FM.a2018.0073. [Epub ahead of print]

Can constant light exposure affect the thyroid gland in prepubertal male albino rats? Histological and ultrastructural study.

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Anatomy and Embryology Department, Faculty of Medicine, Cairo University, Egypt, Egypt.



Through scientific literature, there is evidence that light affects thyroid function in human, mice andrabbits. Constant light and sleep deprivation is also used as a form of human torture, as it has impact on cognitive performances. The present work was conducted to study the effect of constant light for short and long periods on the thyroid gland in the prepubertal male albino rats.


A total of 30 prepubertal male albino rats were used. The rats separated under three groups, group I (control), group II were those rats put under steady encompassing light (24 h/day, light intensity of 600 lux) for four weeks. Group III were the rats maintained in constant light for three months. The rat thyroid gland was subjected to histological and ultrastructural examination.


The rats exposed to light for long durations showed disturbed architecture; the follicles exhibited back to back arrangement (signs of hypertrophy with hyperplasia), lined by multiple layers of follicular cells or were lined by vacuolated cells. Few thyroid follicles were exhibited cystic hyperplasia. Congested blood capillaries were demonstrated between the follicles.


It can be concluded that the short period of constant light for one month had more or less no apparent effect on thyroid gland tissues while longer light periods for three months brought on detrimental outcomes on the thyroid gland structure of male albino rats.


constant light; prepubertal rats and thyroid gland ultrastructural; thyroid gland histological

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