Effects of induced maternal hypothyroidism on the postnatal development of albino rat visual cortex and the ameliorative effect of Levothyroxine

Abstract

Background: Central nervous system (CNS), in particular, depends on thyroid hormones (TH) for the growth and upkeep of normal physiological processes. The preferred medication for thyroid replacement therapy continues to be levothyroxine, a synthetic thyroid hormone. Objectives: The goal of the current study was to determine whether maternally induced hypothyroidism could have an impact on the postnatal development of albino rat visual cortex and whether levothyroxine might have any protective effects or not. Material and Methods: Twenty one (21) pregnant rats were randomly divided equally into three groups; control group (received distilled water orally daily from first day of gestation until day 20 after delivery), hypothyroid group (received Carbimazole orally in a dose of 5 mg/rat/ day from first day of gestation until day 20 after delivery) and hypothyroid group treated with levothyroixine (received Carbimazole orally in a dose of 5mg/ rat/ day for the same period concomitantly with Levothyroxine subcutaneously at a dose of 5µg/day/rat from day 10 of gestation until 20 day after delivery). Pups (newborn, 10 and 20 days) were anesthetized, sacrificed; their brains were processed for histological evaluation. Morphometric and statistical studies were done. Results: Hypothyroidism induced visual cortex histological insults in the form of decreased cortical thickness and nuclear size and increase in packing of cells. Darkly stained cells were noticed. Clustering of pyramidal cells in ganglionic layer was not evident. Borders between layers couldn’t be easily distinguished. These insults were ameliorated in hypothyroid rats treated with Levothyroxine. Conclusion: Levothyroxine might protect against maternal hypothyroidism induced visual cortical neurotoxicity.

Keywords

• maternal hypothyroidism; visual cortex; levothyroxine