Influence Ovariectomy on Parathyroid Gland Function in Local Bitches

Background and Aims: The present study was conducted to assess the effect of ovarian function on the parathyroid gland in local breed bitches in the center of Al-Diwaniyah city, Iran. Materials and Methods: The experiment was carried out on 21 local breed female bitches aged 18 to 30 months housed in the small animal housing of the College of Veterinary Medicine. The animals were divided into three groups of seven each: G1, animals in estrus phase, G2, animals in anestrus phase, and G3, the ovariectomized group. After expressed consent of the owners, ovariectomy was performed immediately after anesthetization. Blood samples were collected to analyze the levels of estrogen, PTH, calcitonin, serum calcium, ionized calcium and 1,25-dihydroxyvitamin D3. Results: Our results in respect of estrogen and PTH revealed a significant effect in G3 and G2 groups as compared with G1 group at p<0.01. The concentration of calcitonin recorded insignificant decrease in G3, 5.35 pg/mL, when compared with G1 which was 6.98 pg/mL. The lowest serum calcium level was recorded in group G3, 8.29 mg/dL, and highest in the group G1, 11.21 mg/dL. The lowest concentration of 1,25-dihydroxyvitamin D3 was found in G3, 18.24 mg/dL, while the highest concentration was 39.56 mg/dL found in group G1. Conclusion: We conclude that decrease of estrogen levels leads to low calcium level, and then increase in the level of PTH in the blood. High level of calcium in the blood leads to increased secretion of calcitonin hormone from the thyroid gland, and calcitonin has no significant effect on the calcium regulation under normal conditions. A decrease in estrogen level leads to a low concentration of 1,25-dihydroxyvitamin D3 followed by decrease of the concentration of ionized calcium.