From the Guidelines
The appropriate laboratory workup for this 41-year-old female should include a comprehensive thyroid panel, complete blood count, comprehensive metabolic panel, lipid profile, and additional targeted tests. Specifically, I recommend measuring free T4 and free T3 levels in addition to the already elevated TSH to distinguish between primary hypothyroidism and other thyroid disorders, as suggested by the USPSTF recommendation statement 1. Thyroid antibodies, particularly anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin antibodies, should be checked to evaluate for autoimmune thyroiditis (Hashimoto's disease), which is the most common cause of hypothyroidism in adults. A complete blood count will help assess for anemia, which can contribute to fatigue. A comprehensive metabolic panel will evaluate liver function, which is important given the patient's atorvastatin use, as well as kidney function and electrolyte status, considering the guidelines for statin use 1. A fasting lipid profile should be obtained to reassess cholesterol levels and determine if the current atorvastatin dose is adequate. Given the palpitations, an electrocardiogram (ECG) would be appropriate to rule out cardiac arrhythmias. The combination of elevated TSH with symptoms of fatigue suggests hypothyroidism, while palpitations could indicate periods of thyroid hormone excess or cardiac issues, as described in the spectrum of thyroid dysfunction 1. This pattern, along with sudden weight loss, raises concern for possible thyroiditis or fluctuating thyroid function. The workup will help determine if thyroid hormone replacement therapy is needed and guide adjustments to the patient's cholesterol management. Key points to consider in the workup include:
- Measuring free T4 and free T3 levels to distinguish between primary hypothyroidism and other thyroid disorders
- Checking thyroid antibodies to evaluate for autoimmune thyroiditis
- Assessing liver function and kidney function due to atorvastatin use
- Reassessing cholesterol levels to determine if the current atorvastatin dose is adequate
- Ruling out cardiac arrhythmias with an ECG
- Considering the spectrum of thyroid dysfunction and potential for thyroiditis or fluctuating thyroid function.
From the Research
Laboratory Workup for Thyroid Dysfunction
The patient's symptoms, such as sudden weight loss, elevated TSH, fatigue, palpitations, dizziness, and a history of hypercholesterolemia, suggest thyroid dysfunction. The following laboratory tests are recommended:
- TSH (Thyroid-Stimulating Hormone) assay to confirm elevated levels 2, 3, 4, 5
- Free T4 (FT4) or its equivalents to assess thyroid hormone levels 2, 3, 4, 6
- Total and free triiodothyronine (TT3 and FT3) to evaluate thyroid hormone levels 2, 3, 4, 6
- Thyroid autoantibodies (TAb), including thyroid-stimulating antibody (TSAb), to diagnose autoimmune thyroid disease 2, 3
- Plasma thyroglobulin (Tg) to assess thyroid function and diagnose thyroid disorders 2
Additional Tests
Depending on the results of the initial tests, additional laboratory investigations may be necessary, such as:
- TSH response to TRH (Thyrotropin-Releasing Hormone) to diagnose subclinical hyperthyroidism or hypothyroidism 2, 6
- Thyroid uptake and scan to evaluate thyroid nodules or hyperthyroidism 2, 3
- Ultrasound to assess thyroid gland structure and diagnose nodular disease 3
Interpretation of Test Results
The interpretation of thyroid function tests requires consideration of the patient's clinical presentation, medical history, and laboratory results. A sensitive TSH assay is the best initial test for screening or case finding, and additional tests should be ordered based on the TSH result 2, 3, 4, 5. The patient's history of high cholesterol and use of atorvastatin should also be considered when interpreting laboratory results. The patient's daily use of marijuana and cigarettes may also impact thyroid function and should be taken into account when evaluating laboratory results 2, 3, 4, 5.