Hypothyroidism due to meds and oth exogenous substances

This code signifies a state of underactive thyroid gland function that is directly caused by the intake of medications or exposure to other external substances. It describes a secondary form of hypothyroidism where an exogenous agent interferes with thyroid hormone production or release.

Apply this code when documentation clearly links a patient's hypothyroidism to a specific drug (e.g., amiodarone, lithium, interferon-alpha) or other external chemical exposure. This diagnosis requires a physician's statement identifying the exogenous substance as the etiology.

• Always sequence this code first if the medicament/substance is the primary reason for the encounter and the hypothyroidism is the main focus of treatment.
• Do not confuse with congenital hypothyroidism or other forms of acquired hypothyroidism not related to exogenous factors.
• Ensure the medical record explicitly states the causative medication or substance; otherwise, a more general hypothyroidism code may be appropriate.