Hormones are chemical messengers that are secreted by glands and regulate many functions as part of the endocrine system in the body. Hormone disorders occur when a gland produces too much or too little of a hormone. Hormone disorders can be caused by many things, including being exposed to certain chemicals in the environment.
Tracking hormone levels in populations provides information on trends and changes of these levels over time. This information may help identify potential causes for hormone level changes in populations, including exposure to environmental chemicals that can affect the endocrine system. Some of the endocrine disrupting chemicals found in the environment include certain pesticides, and industrial chemicals, such as perchlorate, polychlorinated biphenyls (PCBs), and perfluoroalkyl substances (PFAS).
Data on thyroid hormone function on the Tracking Network comes from CDC’s National Health and Nutrition Examination Survey (NHANES). NHANES is an ongoing, complex survey that samples the U.S population. It collects different types of information to provide an assessment of the population’s overall health and nutrition. The data in each measure are derived from urine and blood samples from people who are typical examples of the U.S. population. The data are available for the United States as a whole, not by county, state, or region.
Population Thyroid Hormone Levels
This indicator shows concentrations of different thyroid hormones in blood, including thyroxine (T4), triiodothyronine (T3), and thyroid stimulating hormone (TSH). This indicator also shows concentrations of iodine in urine.
Some limitations of the data and measures on the Tracking Network are:
- The measures cannot be used to provide population reference levels or trends over time for thyroid in children younger than 12 years, as NHANES did not measure thyroid hormones in children younger than 12 years.
- The measures cannot be used to provide population reference levels or trends over time for thyroid hormones or urinary iodine in pregnant women as not enough pregnant women were sampled to produce population-based estimates of thyroid hormones or urinary iodine for pregnant women.
Data available on the Tracking Network on thyroid hormone function can be used to:
- Provide reference levels of thyroid hormone levels in the US population
- Provide trends over time of thyroid hormone levels in the US population
- Provide information on adequacy of iodine levels in US population and inform interventions for iodine inadequacy (e.g., requirements for supplements)
- Provide trends of urinary iodine levels over time in the US populations