What laboratory tests are typically ordered for a patient visiting an endocrinologist?

From the Guidelines

Endocrinologists typically order a comprehensive set of laboratory tests tailored to the patient's specific symptoms and suspected condition, with common baseline tests including a complete blood count (CBC), comprehensive metabolic panel (CMP), lipid panel, and thyroid function tests (TSH, free T4, and sometimes free T3) 1. When evaluating patients, endocrinologists often prioritize tests that can detect abnormalities in thyroid function, as thyroid disorders are common and can have significant impacts on morbidity, mortality, and quality of life.

Common Laboratory Tests

Some of the key laboratory tests that may be ordered for a patient visiting an endocrinologist include:

• Complete blood count (CBC)
• Comprehensive metabolic panel (CMP)
• Lipid panel
• Thyroid function tests (TSH, free T4, and sometimes free T3) 1
• Fasting blood glucose
• Hemoglobin A1C
• Glucose tolerance test (occasionally)
• Hormone-specific tests, such as:
  • Cortisol levels (morning or 24-hour urine collection)
  • ACTH
  • Prolactin
  • Growth hormone
  • IGF-1
  • Testosterone
  • Estradiol
  • FSH
  • LH
  • Parathyroid hormone (PTH) with calcium levels
• Adrenal function tests, such as:
  • DHEA-S
  • Aldosterone
  • Renin measurements These tests help endocrinologists diagnose conditions like diabetes, thyroid disorders, adrenal insufficiency, pituitary disorders, and reproductive hormone imbalances, and allow them to identify hormone imbalances that may be causing the patient's health issues.

Importance of Thyroid Function Tests

Thyroid function tests, particularly the TSH test, are highly sensitive and specific for detecting thyroid dysfunction, with a sensitivity of about 98% and a specificity of about 92% when used to confirm clinically suspected thyroid disease in patients referred to an endocrinologist 1. However, the accuracy of TSH screening in asymptomatic persons is more challenging to ascertain, and the test's results can be influenced by various factors, such as age, sex, and race/ethnicity, as well as certain medications and substances.

Tailoring Tests to the Patient's Needs

The specific combination of tests ordered depends on the patient's presenting symptoms, medical history, and physical examination findings, allowing the endocrinologist to tailor the diagnostic workup to the individual patient's needs and suspected condition. By prioritizing the most relevant and sensitive tests, endocrinologists can efficiently diagnose and manage hormone-related disorders, ultimately improving patient outcomes and quality of life.

From the Research

Laboratory Tests for Endocrinology Patients

The following laboratory tests are typically ordered for patients visiting an endocrinologist:

• Thyroid function tests:
  • Thyroid-stimulating hormone (TSH) 2, 3
  • Free thyroxine (FT4) 2, 3
  • Free triiodothyronine (FT3) 3
  • Thyroid peroxidase antibodies (TPO-Ab) 2, 3, 4
• Diabetes screening and monitoring:
  • Fasting plasma glucose (FPG) 5
  • Oral glucose tolerance test (OGTT) 5
  • Glycohemoglobin (HbA1c) 5
  • Microalbuminuria screening 5
• Lipid profile:
  • Total cholesterol 6
  • High-density lipoprotein (HDL) cholesterol 6
  • Low-density lipoprotein (LDL) cholesterol 6
  • Triglycerides 6
• Other tests:
  • Thyroglobulin (Tg) 3
  • Thyroglobulin antibodies (Tg-Ab) 3
  • TSH receptor antibodies (TRAb) 3
  • Calcitonin 3

Specific Conditions and Tests

Certain conditions may require additional or specific laboratory tests, such as:

• Hashimoto's thyroiditis: TPO-Ab and Tg-Ab 3
• Graves' disease: TRAb 3
• Medullary thyroid carcinoma: Calcitonin 3
• Gestational diabetes mellitus: 100-g, 3-hour OGTT or plasma glucose 1 hour after a 50-g oral glucose load 5
• Metabolic syndrome: Thyroid function tests, lipid profile, and glucose screening 6