The incidence of postradiation hypothyroidism is hard to determine, as the literature is quite varied. This variation is due to a combination of how hypothyroidism is measured, how much of the thyroid was treated, and when patients were assessed. Recent literature suggests the incidence can approx...

Radiation induced hypothyroidism (RIHT) is common. As described by @Adam S. Garden and @Hong Zhang, the incidence varies in literature. We analyzed 117 pts at VCU, with median Fu of 3 years, 32% developed RIHT (> 5.5), median time is 18 months after RT; nearly 1/3 were detected in the 1st ye...

Incidence of radiation induced hypothyroidism after radiation to the cervical neck has been reported to be around 20 to 30%.  Most patients develop hypothyroidism within the first 5 years of follow-up.   Although the exact dose response remains elusive, most studies indicate that the ...