What is the main characteristic of cretinism?

Cretinism is primarily a result of severe iodine deficiency during prenatal development or early life, leading to a critical shortage of thyroid hormones, particularly thyroxine (T4). This deficiency has profound effects on physical and cognitive development. The hallmark characteristic of cretinism is mental retardation, which occurs due to the impact of inadequate thyroid hormone on brain development. In addition to cognitive impairment, individuals with cretinism may also exhibit physical features such as short stature and disproportionate body growth, but these are secondary to the primary issue of intellectual development.

The other choices do not accurately capture the essence of cretinism. Excessive height would not be characteristic; in fact, individuals often present with short stature due to developmental delays. Delayed puberty is not a primary characteristic of cretinism but can occur as a consequence of overall developmental delays. Lastly, an increased metabolic rate would be inconsistent with the condition, as thyroid hormone deficiency typically leads to a decreased metabolic rate, further complicating physical growth and development.