Hashimoto's disease is the leading cause of hypothyroidism in the United States. This autoimmune disease causes an underactive thyroid. Magnesium often is recommended by nutritionists as a nutrient that supports thyroid function. If you suspect you are deficient in magnesium, consult your health-care provider for a proper diagnosis and to determine if supplements are warranted.

Hashimoto's Disease

Hashimoto's disease most often affects middle-aged women. However, this disease, also called chronic lymphocytic thyroiditis, also can affect men. With Hashimoto’s, your thyroid becomes inflamed because your immune system makes antibodies that attack your thyroid cells. This inflammation frequently leads to an underactive thyroid, or hypothyroidism. Symptoms of hypothyroidism include pale and dry skin, constipation, fatigue, cold sensitivity, a hoarse voice, puffy face, unexplained weight gain, elevated cholesterol, muscle stiffness and aches, joint pain, muscle weakness, depression and excessive or prolonged menstrual bleeding.

Magnesium Significance

Your thyroid makes hormones called T3 and T4. These regulate how your body uses energy. When your thyroid is underactive, these thyroid hormone levels become too low. Magnesium is important for thyroid support because your body needs it to activate T4 hormone into T3, according to “The Natural Hormone Makeover,” by physician Phuli Cohan.

Supplementation and Considerations

In case of deficiency, magnesium supplementation sometimes helps alleviate some of the symptoms of thyroid disease, according to “Principles of Orthomolecularism,” by urologist R. Hemat. However, always consult a doctor to determine a treatment plan for your Hashimoto's disease. If you do not have evidence of hormone deficiency, your doctor may recommend a wait-and-see approach. However, you may need replacement therapy with thyroid hormone, according to MayoClinic.com. If not properly treated, your symptoms of underactive thyroid may worsen. Untreated hypothyroidism can cause numerous problems including infertility, high cholesterol, miscarriage and birthing a baby with birth defects. Rarely it can cause seizures, heart failure, coma or death, according to WomensHealth.gov.

Amounts and Deficiency Signs

Nutritionists who recommend magnesium supplementation advise taking varying doses to support thyroid function, from 200 milligrams twice daily for a total of 400 milligrams to a daily dose of 800 milligrams. Consult a health-care provider to determine what dose of supplemental magnesium, if any, is appropriate for you. Magnesium is found in many foods including almonds, halibut, cashews, spinach, oatmeal, brown rice and peanuts. The recommended daily intake for magnesium is 310 milligrams daily if you are female and 400 milligrams if you are male, up to age 30. At age 31 and over, the recommendation is 320 milligrams for women and 420 milligrams for men.

Early signs of magnesium deficiency include appetite loss, fatigue, nausea, vomiting and weakness. Later signs include tingling, muscle cramps and contractions, seizures and abnormal heart rhythms. Certain medications, including diuretics and antibiotics, raise your risk for magnesium deficiency. Age, malabsorptive problems like gluten-sensitive enteropathy and other factors, like low calcium or potassium levels, also your raise risk.