In non iodine-deficient communities, primary hypothyroidism is ten times more common in women than in men. The prevalence in women of all ages is two to four per cent of the population (with one-third of these cases presenting with iatrogenic hypothyroidism). The annual incidence of primary hypothyroidism in women of all ages is two per thousand population. It is most common in middle- aged women, but can occur at any age.
The incidence of hypothyroidism following radioiodine therapy is highest during the first year after treatment, regardless of the dose of 131I, but continues to accumulate slowly and may reach fifty per cent after ten years (Fig. 15.22).
