What laboratory tests are recommended for evaluating immune or endocrine disorders?

From the Guidelines

When evaluating a patient for immune or endocrine disorders, the most pertinent laboratory tests to order include thyroid function tests (TSH, free T4, free T3), adrenal function tests (cortisol, ACTH stimulation test), glucose metabolism tests (fasting glucose, HbA1c, insulin levels), reproductive hormone panels (FSH, LH, estradiol, testosterone, progesterone), and pituitary function tests (prolactin, growth hormone), as recommended by the most recent guidelines 1.

For immune disorders, the following tests are recommended:

• Complete blood count with differential to assess white blood cell populations
• Immunoglobulin levels (IgG, IgA, IgM, IgE) to evaluate antibody production
• Complement levels (C3, C4, CH50) to assess complement system function
• Autoantibody panels such as ANA, anti-dsDNA, and RF for autoimmune conditions
• Flow cytometry to analyze lymphocyte subsets
• Functional immune tests like lymphocyte proliferation assays to assess immune cell responses

For endocrine disorders, the following tests are recommended:

• Thyroid function tests (TSH, free T4, free T3)
• Adrenal function tests (cortisol, ACTH stimulation test)
• Glucose metabolism tests (fasting glucose, HbA1c, insulin levels)
• Reproductive hormone panels (FSH, LH, estradiol, testosterone, progesterone)
• Pituitary function tests (prolactin, growth hormone)

It is essential to note that the interpretation of these tests requires consideration of reference ranges, which vary by laboratory, age, sex, and sometimes time of day due to hormonal circadian rhythms 1.

When to refer to a specialist:

• If the patient presents with symptoms of pituitary dysfunction, such as headache, visual changes, or fatigue, referral to an endocrinologist is recommended 1.
• If the patient develops signs of adrenal insufficiency, such as hypotension, referral to an endocrinologist is recommended 1.
• If the patient develops signs of thyroid dysfunction, such as hyperthyroidism or hypothyroidism, referral to an endocrinologist is recommended 1.

In summary, a comprehensive approach to evaluating immune and endocrine disorders involves ordering a range of laboratory tests tailored to the specific suspected condition, considering reference ranges and hormonal circadian rhythms, and referring to a specialist when necessary, as supported by the most recent guidelines 1.

From the Research

Laboratory Tests for Immune or Endocrine Disorders

When evaluating immune or endocrine disorders, several laboratory tests are recommended. The following tests are pertinent to get:

• Biochemical analyses for endocrine diseases such as diabetes, thyroid dysfunction, male hypogonadism, and adrenal insufficiency 2
• Blood tests for thyroid-stimulating hormone (TSH), free thyroxine, free triiodothyronine, thyroglobulin (Tg), thyroglobulin antibodies (Tg-Ab), thyroid peroxidase antibodies (TPO-Ab), TSH receptor antibodies (TRAb), and calcitonin for thyroid disorders 3

Tests to Order for a Specialist

For a specialist, the following tests may be ordered:

• TPO-Ab and TRAb tests to diagnose Hashimoto's thyroiditis and Graves' disease, respectively 3
• Tg and calcitonin as tumor markers for differentiated thyroid carcinoma and medullary thyroid carcinoma (MTC), respectively 3
• Procalcitonin as a potential biomarker for MTC 3

Considerations for Test Interpretation

When interpreting test results, it is essential to consider the clinical context, including:

• Possible assay interferences and/or the effects of concurrent medications 3
• The presence of pregnancy or critical illness, which may affect thyroid function test results 3
• The role of physical examination in identifying clinical manifestations of endocrine diseases and guiding diagnosis 4