| Noun | 1. | hypothyroidism - an underactive thyroid gland; a glandular disorder resulting from insufficient production of thyroid hormonesmyxedema, myxoedema - hypothyroidism marked by dry skin and swellings around lips and nose as well as mental deterioration cretinism - severe hypothyroidism resulting in physical and mental stunting hyperthyroidism, thyrotoxicosis - an overactive thyroid gland; pathologically excessive production of thyroid hormones or the condition resulting from excessive production of thyroid hormones | |