先天性甲状腺机能低下症(congenital hypothyroidism (CH))是指出生时缺乏甲状腺激素的一种症状。大约每4千位新生儿中会有一位新生儿的甲状腺机能有严重的缺陷，其他有更多的新生儿有轻微或程度不一的缺陷。若出生后数个月不予治疗，严重的先天性甲状腺机能低下症可能会导致生长障碍及永久的智能障碍。治疗的方式为每天口服固定剂量的甲状腺素。因为治疗简单、有效且便宜，几乎所有的已开发国家都会实施新生儿筛检好在出生后头几个礼拜内发现并治疗先天性甲状腺机能低下症。

Congenital hypothyroidism (CH) or cretinism is a condition of thyroid hormone deficiency present at birth. Approximately 1 in 4000 newborn infants has a severe deficiency of thyroid function, while even more have mild or partial degrees. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability. Treatment consists of a daily dose of thyroid hormone (thyroxine) by mouth. Because the treatment is simple, effective, and inexpensive, nearly all of the developed world practices newborn screening to detect and treat congenital hypothyroidism in the first weeks of life.