**Core Concept**
Thyroid-stimulating immunoglobulins (TSI) are autoantibodies that mimic the action of thyroid-stimulating hormone (TSH) by binding to the TSH receptor on thyroid cells, leading to uncontrolled thyroid hormone production. This is a key concept in the pathogenesis of Graves' disease.

**Why the Correct Answer is Right**
The correct answer, **B. Antibody to thyroid cell receptors**, refers to the specific mechanism by which TSI antibodies cause thyroid hyperstimulation. These antibodies bind to the TSH receptor on the surface of thyroid cells, activating the receptor and stimulating the production of thyroid hormones. This binding is highly specific and results in an exaggerated response, leading to hyperthyroidism. The TSH receptor is a G protein-coupled receptor that, when activated, stimulates the production of cyclic AMP (cAMP) and ultimately leads to the release of thyroid hormones.

**Why Each Wrong Option is Incorrect**
**Option A:** Antibody to thyroid globulin refers to anti-thyroglobulin antibodies, which are found in autoimmune thyroiditis (e.g., Hashimoto's thyroiditis) and are not directly involved in thyroid hormone production.

**Option C:** Antibody to thyroxine refers to anti-thyroxine antibodies, which are typically found in autoimmune thyroiditis and are not responsible for stimulating thyroid hormone production.

**Option D:** Antibody to thyroid cells refers to a broad category of autoantibodies that target thyroid cells, but does not specifically describe the mechanism of action of TSI antibodies.

**Clinical Pearl / High-Yield Fact**
Graves' disease is the most common cause of hyperthyroidism in adults and is characterized by the presence of TSI antibodies. These antibodies can be detected in the serum of affected individuals and are a key diagnostic marker for the condition.

**✓ Correct Answer: B. Antibody to thyroid cell receptors**