Serum Level of Thyroid Stimulating Hormone, Triiodothyronine, Thyroxin and Weight Rate in Caucasian Pit Viper (Viperidae: Gloydius Halys Caucasicus) of Iran during Different Seasons

In this research, concentration of thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxin (T4) and their relationship with body weight in Caucasian viper have been studied. The female Caucasian pitviper (n=26) were collected from Lar in Tehran province, the animal's body weight and length, and serum TSH, T3 and T4 levels were measured by electrochemiluminescence method during autumn, winter and summer in year 2014. The results showed T3 hormone concentration in autumn was 0.74± 0.06 nmol/Lt that was higher than its level in winter, 0.46± 0.8 nmol/Lt (P≥0.05) and no significant different with its concentration in summer 0.76 ± 0.05 nmol/Lt. The concentration of T4 hormone in autumn, 0.84±0.28 nmol/Lt was higher than winter 0.76±0.033 nmol/Lt (P≥0.19) and also summer 0.64 ±0.018 nmol/Lt (P≥0.001). TSH concentration was 0.005 nmol/Lt in autumn; reach to 0.013±0.008 nmol/Lt in winter and again 0.005 nmol/Lt in summer that shows relative increase in winter (P≥0.05). Mean body length and weight of female Caucasian vipers were 47.50±0.69 cm and 50.80±2.53 gram in autumn and 34.33±2.33 cm, 43.33±2.40 gram in winter and 51.64±1.26 cm and 64.78±3.47 gram in summer, respectively. This is indicated that Caucasian vipers' body weight is decreased in winter could be because of body fat consumption, inaccessibility to food and beginning of reduction of nutritional activity at the end of autumn compare to summer that may result to lower body weight in winter. Concentration of T3 and TSH hormone is decreased in summer and increased in winter. It seems by decreasing temperature in winter serum concentration of TSH is increased and viper`s body weight reduced (Fat consumption) to provide required energy and heat for Iranian Caucasian viper survival. So, seasonal and temperature variation has significant effect on Iran Caucasian viper`s thyroid hormones that is important for animal maintenance. Although further study is needed.