CASE #2 A 40-year-old female went to her physician because she was feeling tired

Question

CASE #2 A 40-year-old female went to her physician because she was feeling tired all the time. She had gained about 10 pounds in the last few months and exhibited some facial puffiness. Her thyroid gland was enlarged and rubbery. Laboratory results were as follows: Studies Hemoglobin S-TSH Free thyroxine (fT) 0.8 ng/mL 1.0-2.0 ng/mL Value 12.7 g/dL 7.7 ?U/mL Normal Range 12-16 g/dL 2.3.4.0 ?U/mL Anti-TPO 715 IU/mL 10.0 IU/mL 1. What is the likely diagnosis in this case (be specific)? Explain your reasoning for this decision. (2) 2. What other antibody(ies) would likely be found in this condition? Should a test for this/these antibody(ies) be performed to confirm diagnosis? Explain your reasoning. (2) 3. Explain the specific mechanism of how anti-TPO effects thyroid function? (I) 4. In what other condition can anti-TPO be found? How can this condition be differentiated from the condition experienced by this patient? (1.5)

Explanation / Answer

Solutions

1. The s-TSH (serum Thyroid-stimulating hormone) of the patient is above normal levels, while the free thyroxine is below the normal levels. The most defining parameter is the high levels of Anti-TPO antibodies, which are way above normal. The most common cause is autoimmune thyroid disease. The antibodies attack the thyroid gland, which leads to its malfunction, and subsequently leads to hypothyroidism.
The most likely diagnosis is Hashimoto’s Thyroiditis.

2. In order to confirm the diagnosis , the most commonly analyzed antibodies include Anti-thyroid antibodies (ATA) tests, such as the microsomal antibody test (also known as thyroid peroxidase antibody test) and the anti-thyroglobulin antibody test. These tests are required to understand the root cause behindthe hypothyroidism. In patients with auto immunity against thyroid gland, immune cells attack the thyroid tissue, and in the process produce antibodies. Detection and quantization of these antibodies are necessary to make a precise diagnosis.

3. Thyroperoxidase (TPO) is an enzyme involved in synthesis of triiodothyronine and thyroxine (tetraiodothyronine). Since TPO is attacked by antibodies, T3 and T4 levels fall down. This creates a feedback loop in which the pituitary gland in the brain will make more TSH, because it thinks the thyroid is not making enough thyroid hormone.

4. Apart from Hashimoto’s thyroiditis, auto-antibodies against the thyroid are also found in Grave’s disease. In such cases, one needs to test for thyrotropin receptor antibodies (TRAbs), which are present in 70-100% of Graves' disease cases.

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