Maternal Hypothyroidism Influences the Weight of Brain and Impairs the Migration of Neurons Inside the Hippocampus of Neonatal Rat

Objective: To histologically observe the effects of hypothyroidism on the hippocampus of neonatal rats. Methods: A total of 10 healthy female Wistar rats, between 12-16 weeks old, were randomly divided into 2 groups; Group A was labelled as control and Group B was made hypothyroid by giving 15mg/kg of Propylthiouracyl (PTU) daily mixed in chow. The treatment was continued for a week before they were allowed to mate and conceive, and it was not interrupted throughout pregnancy and delivery until 21st day of lactation. On the 22nd day, 10 pups from each of the two groups were euthanized; 3cc of blood was drawn out from the heart immediately and the brains were scooped out, weighed, fixed in formalin after slicing out the cerebrum along with hippocampus, processed and stained to observe the arrangement and count and number of pyramidal neurons of CA3 region of hippocampus. Results: There was a significant decrease in the brain weights of group B pups (1.21 ± 0.21mg) when compared to the control group A (1.42 ± 0.01mg). The thyroxine (T4) level from the experimental group B was significantly decreased (27.7 ±1.2 ng/dl) compared to control (32.1 ± 0.9 ng/dl). Moreover, the serum levels of TSH were significantly higher in group B (21 ± 3.7ng/dl) as compared to group A (15 ± 2.4 ng/dl). The number of pyramidal cell count in group B was significantly decreased (39 ± 1.24 per unit area) as compared to group A (44 ± 2.49 per unit area). Conclusion: Maternal hypothyroidism not only exerts its' influence on the arrangement of Pyramidal neurons of CA3 area of hippocampus, but it also decreases their count. Overall, it effects the weight of the brain and significantly raises the levels of TSH in the neonates.