Difference between Hashimotos Thyroiditis and Graves Disease

Hashimoto’s thyroiditis is an autoimmune thyroid disorder that may be associated with a goiter (thyroid lump) or in late stages of the disease with minimal residual thyroid tissue (atrophic thyroiditis).

The autoimmune process of Hashimoto’s thyroiditis causes reduced thyroid function.  The body reacts by initiating a compensatory phase in which the TSH rises to continue promoting adequate release of the thyroid hormone T4.  The condition of elevated TSH with normal thyroid hormone levels is called subclinical hypothyroidism and is usually asymptomatic or associated with only minor symptoms. 

Eventually, the T4 hormone levels will fall despite very high TSH levels (over 10mU/L).  People with Hashimoto’s will then become symptomatic.  The condition of high TSH with low T4 levels is known as clinical hypothyroidism or overt hypothyroidism.

The asymptomatic compensatory phase of Hashimoto’s thyroiditis can last for quite some time such that many people initially present to their physicians with a thyroid mass rather than symptoms of hypothyroidism. 

The goiter in Hashimoto’s thyroiditis is an irregular, firm nodule in the thyroid area (either side of the trachea or “wind pipe” near the bottom of the throat).  Goiters can become large enough to produce a visible asymmetry of the neck. 

Grave’s disease is another autoimmune thyroid disorder that can cause goiter formation.  It is common for students of health sciences to forget the differences between Grave’s disease and Hashimoto’s thyroiditis.  However, these two autoimmune thyroid conditions result in drastically different clinical pictures, require different treatments and have different outcomes.

Hashimoto’s hypothyroidism results from the production of antibodies that destroy thyroglobulin and/or the enzyme thyroid peroxidase.  Thyroglobulin is a protein used by the thyroid gland to produce the thyroid hormones T3 and T4.  Thyroid peroxidase is an enzyme in the thyroid that assists in the production of T3 and T4.

Grave’s disease, on the other hand, causes an autoimmune hyperthyroidism.  Grave’s disease is actually the most common cause of hyperthyroidism.  The excessive thyroid activity of Grave’s disease is the result of autoantibodies to the TSH (thyroid stimulating hormone) receptor.  The TSH receptor antibodies activate the TSH receptors and stimulate the thyroid to produce excessive amounts of thyroid hormone.

Thus, the key difference between the autoimmune thyroid disorders Hashimoto’s and Grave’s disease lies in the action of the autoantibodies that are produced. 

-Hashimoto’s autoantibodies decrease precursors necessary for thyroid hormone production, thereby causing hypothyroidism. 

-Grave’s disease autoantibodies stimulate TSH receptors, thereby increasing thyroid hormone production and causing hyperthyroidism.