Serum TSH and Total T 4 in the United States Population and Their Association With Participant Characteristics: National Health and Nutrition Examination Survey (NHANES 1999–2002)

Associations with known factors such as age, race, and sex were confirmed using this data set. Understanding the prevalence of abnormal thyroid tests among reproductive-aged women informs decisions about screening in this population. The finding that individuals on thyroid hormone replacement medication often remain hypothyroid or become hyperthyroid underscores the importance of monitoring.