Complete absence of the thyroid gland at birth, a rare congenital condition.
From Greek 'a-' (without) + 'thyrá' (relating to thyroid) + '-osis' (condition), literally 'the condition of being without a thyroid.'
Athyrosis was a death sentence before synthetic thyroid hormone was invented in 1891—babies born without thyroids would develop severe mental disability and stunted growth, making this one of the clearest examples of modern medicine rescuing children from biological disaster.
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