• Hayat NQ Hayat
  • Tahir M Tahir
  • Munir B Munir
  • Sami W Sami


Background: The current study was carried out to investigate the effect of hypothyroidism on thehistological structure of parotid salivary gland of the rat. Methods: Twenty male albino rats, weighingbetween 130–150 grams, were used which were divided into two groups; control group (A) and anexperimental group (B), each containing 10 animals. Group B was rendered hypothyroid by givingmethimazole (MMI) as 0.02% solution in drinking water daily for 3 weeks. On day 22nd parotid andthyroid glands were removed, weighed and processed for light microscopy. Salivary gland was fixed inBouin’s solution, H&E and Toluidine blue stains were used for histological examination. Serum T3, T4and TSH levels were determined by enzyme immunoassay. Results: In group A, serum concentrationof T3, T4 and TSH was 12.58±3.05 ηg/ml, 4.72±1.20 µg/dl, and 0.25±0.24 µIU/ml respectively, whereas in group B it was 2.14±1.83 ηg/ml, 1.04±0.44 µg/dl and 1.44±0.20 µIU/ml respectively. Whendifferences between T3, T4 and TSH of the groups were compared, the p-value was <0.000, <0.000, and<0.000 respectively. Mean thyroid weight significantly increased in group B (44.1 0±1.66 mg) whencompared to that in group A (33.70±1.56 mg). These findings established the occurrence ofhypothyroid state in the experimental group. There was a statistically significant reduction in the parotidgland weight in the animals of the experimental group (38.30±1.15 mg) when compared to the controlgroup (39.60±0.84 mg), (p<0.01). With light microscopy, group A showed a normal structure ofparotid salivary gland, whereas multiple histological changes were observed in parotrid gland of theexperimental group. Number of mast cells in parotid gland was also significantly higher (p<0.017) ingroup B (3.70±1.11/mm2) than in group A (2.25±1.34/mm2). Conclusion: The level of T3, T4 decreasedand that of TSH increased in the experimental group when compared with control group; there werealso changes in the histological structure of the parotid salivary gland.Keywords: Methimazole, parotid gland, hypothyroidism, histology, rat


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