High levels of growth hormone accelerate mitosis rate but decrease the apoptosis process in its target organs. These events might cause the initiation of different cancer types. Thus, the main aims of this study were assessing the effects of short term growth hormone administration and resistance training on the histopathology and detection of the BRAF-V600E mutation in the thyroid tissue of male Rattus norvegicus brown rats. Thirty-two rats were randomly divided into four groups. After 8 weeks of the experiment (i.m), thyroid tissue and blood samples of saline (CS), resistance training+saline (RS), growth hormone (2 mg/kg) (GI) and resistance training+growth hormone (2 mg/kg) (RG) were taken to evaluate histopathology, the BRAF T1799A mutation of thyroid tissue, and circulating levels of IGF-1 and IGFBP-3. The protocol of training consisted of rats climbing a ladder while carrying weights (3 sets/5 reps). Microscopic evaluation of thyroid tissue did not show any histopathological changes, and there were no mutations in the studied region of the BRAF sequence. Serum IGF-1 concentration was significantly lower in the RS group than in other groups (P<0.05). However, serum IGFBP-3 concentration did not change significantly in the RS group. Moreover, serum IGF-1 and IGFBP-3 concentrations were significantly higher in the GI and RG groups than in the others (P<0.05). In conclusion, the decrement of serum IGF-1 concentration and IGF-1/IGFBP-3 ratio after resistance training might decrease the risk of cancer. Furthermore, short term growth hormone administration, with and without resistance training, might increase the risk of cancer through the high levels of serum IGF-1 concentration and IGF-1/IGFBP-3 ratio in male rats.

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