Chapter 4: How Is Thyroid Disease Diagnosed?

Correctly diagnosing thyroid disorders is now easier than ever before; many advances have been made in tests and equipment over the last two decades. Nonetheless, the most important factors leading to a correct diagnosis remain the patient's medical history and physical examination. Most of the time, a doctor arrives at a correct diagnosis with information from the medical history and physical examination alone. A physician orders tests based upon conclusions drawn from the patient's medical history and physical examination in order to confirm a diagnosis and rule out other possibilities.

One way to understand how a physician diagnoses thyroid disease is to consider the "five~finger rule." Each finger of the hand represents one step taken by a physician to reach a diagnosis.

Figure 4.1 . Five~finger rule.

As with the classification of thyroid diseases described in Chapter 2, there is much overlap between tests of thyroid function and tests of thyroid structure. Furthermore, not all patients will have all tests. For example, a patient will not ordinarily have a thyroid biopsy unless she has a thyroid nodule. Nonetheless, the five~finger rule may prove useful in understanding what is going on at the doctor's office.