A type of primary hypothyroidism, Hashimoto's disease is an autoimmune disorder, in which anti-thyroid antibodies destroy the ability of the thyroid gland to produce the thyroid hormones. Antibodies against thyroid peroxidase (TPO) and thyroglobulin (Tg) are often seen in this disorder.

Hashimoto's disease is also known as Hashimoto's thyroiditis.

Hypothyroidism
Primary hypothyroidism

BMI

The body mass index is measured by dividing body weight (in kilograms) by body height (in meters) squared (kg / m²). It is highly correlated with body composition, and higher BMI values are correlated with higher body fat content. The BMI value is used to classify one's weight in several categories including underweight, normal, overweight, and obese. The range of BMI values considered to be normal is 18.5 to 24.9. Higher BMI values are associated with an increased risk for diseases such as diabetes mellitus type II, hypertension, and cardiovascular disease.

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Body mass index (Wikipedia)

Hyperthyroidism refers to a pathophysiological condition in which the thyroid gland produces and releases abnormally high levels of the thyroid hormones (T₃ and T₄).

The symptoms of hyperthyroidism may include high metabolic rate, weight loss, nervousness, excess heat production, tachycardia, and tremor.

Two main forms of hyperthyroidism exist: (1) Primary hyperthyroidism, and (2) Secondary hyperthyroidism.

In primary hyperthyroidism, the thyroid gland produces high levels of the thyroid hormones, either as a result of a secretory tumor of the thyroid gland, or under the control of thyroid stimulating immunoglobulins (such as in Graves' disease).

Secondary hypothyroidism is caused by high levels of thyroid stimulating hormone (TSH) produced by the anterior pituitary gland. TSH then stimulates the thyroid gland to produce excessive amounts of the thyroid hormones.

Hypothyroidism
Euthyroidism

Primary hypothyroidism is characterized by abnormally low levels of thyroid hormone (T₃ and T₄) production, where the defect is at the level of the thyroid gland itself.

In primary hypothyroidism, the circulating levels of the thyroid hormones are low, however, the levels of the thyroid stimulating hormone (TSH) are high due a lack of thyroid hormone negative feedback on the anterior pituitary.

Common causes of primary hypothyroidism include iodine deficiency (which leads to goiter), and Hashimoto's disease, in which autoimmune antibodies destroy the ability of the thyroid gland to produce the thyroid hormones.

Hypothyroidism
Secondary hypothyroidism
Tertiary hypothyroidism