insufficiently active: an underactive thyroid gland.
- un·der·ac·tiv·i·ty, un·der·ac·tive·ness, noun
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How to use underactive in a sentence
An underactive thyroid, known as hypothyroidism, is caused by an inadequate production of thyroid hormone.When You Don't Know Where to Turn | Steven J. Bartlett
British Dictionary definitions for underactive
(of the thyroid or adrenal glands) not functioning at full capacity
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012