Abstract: Objective: To study the radiation response of the pituitary to single dose irradiation. Methods: The porcine hypophysis was irradiated by single doses with the LINAC SRS system. The serum levels of testosterone,T₃,T₄ and cortisol were mea sured. At the 40 weeks after irradiation, pituitary, testes, thyroids and adrenals were obtained for histopathological examination. Results: The results showed that the serum testosterone levels first declined in all irradiated groups, but recovered in different degree in 5-15Gy groups. In the late stage, the decline of the 20Gy group’s T₄ and testerone levels sustained. No significant changes in T₃ and cortisol levels were found. Conclusion: It suggests that there are different radiative sensitivity among the pituitary endocrine cells. 5Gy irradiation could restain FSH production, but this ability could partly recover even after 15Gy irradiation. After 20Gy single dose irradiation, ACTH-producting cells could maintain normal function, while TSH producting cells should be slightly inhibited.