IUDs Do Not Affect Hypothyroidism
IUDs—both copper and levonorgestrel-releasing devices—can be safely used in women with hypothyroidism without any impact on thyroid function or disease management. 1
Evidence from Guidelines
The U.S. Medical Eligibility Criteria for Contraceptive Use explicitly addresses this question and provides clear guidance:
Women with hypothyroidism are assigned Category 1 for both copper IUDs and levonorgestrel IUDs, meaning there are no restrictions on use and the method can be used without concern. 1
This Category 1 classification applies equally to women with simple goiter, hyperthyroidism, and hypothyroidism, indicating that thyroid disorders of any type do not contraindicate IUD use. 1
No special monitoring, dose adjustments of thyroid medication, or precautions are required when inserting or maintaining an IUD in women with hypothyroidism. 1
Mechanism Considerations
The lack of interaction between IUDs and hypothyroidism is biologically logical:
Copper IUDs work through local effects in the uterus by creating an inflammatory environment that is toxic to sperm and prevents fertilization, with no systemic hormonal effects. 2
Levonorgestrel IUDs release progestin locally with minimal systemic absorption compared to oral contraceptives, and progestins do not interfere with thyroid hormone metabolism or thyroid function. 1, 2
Hypothyroidism is managed with levothyroxine replacement therapy, which is not affected by intrauterine contraceptive devices. 3
Clinical Implications
For women with hypothyroidism seeking contraception:
IUDs represent an excellent contraceptive option with failure rates less than 1% and no need for daily adherence, which is particularly valuable since these women already require daily thyroid medication. 1, 4
Women with hypothyroidism who experience menorrhagia (a common symptom affecting approximately 23% of hypothyroid patients) may particularly benefit from the levonorgestrel IUD, which reduces menstrual blood loss. 2, 3
No additional screening or testing related to thyroid function is needed before IUD insertion in women with known hypothyroidism. 1
Common Pitfall to Avoid
Do not confuse the safety of IUDs in hypothyroidism with the contraindications that exist for combined oral contraceptives in certain other endocrine conditions—IUDs have far fewer contraindications than hormonal pills and are safe across a broad range of medical conditions including all thyroid disorders. 1