What does a Thyroid-Stimulating Hormone (TSH) level of 0.789 indicate?

Interpretation of TSH Level 0.789

A TSH level of 0.789 mIU/L is within the normal reference range (0.45-4.5 mIU/L) and indicates a euthyroid state, requiring no treatment. 1, 2

Understanding TSH Reference Ranges

TSH (Thyroid-Stimulating Hormone) is the primary screening test for thyroid dysfunction with high sensitivity (98%) and specificity (92%). The normal reference range for TSH is generally accepted as 0.45-4.5 mIU/L based on population studies. 1, 2

• The NHANES III study established a reference range of 0.45-4.12 mIU/L in a disease-free population 1
• Values between 0.45-4.5 mIU/L are considered normal and indicate proper thyroid function 2
• A TSH of 0.789 falls comfortably within this normal range

Clinical Significance of This TSH Value

A TSH level of 0.789 mIU/L indicates:

• Normal pituitary-thyroid axis function
• No evidence of clinical or subclinical hyperthyroidism or hypothyroidism
• No need for additional thyroid testing unless clinically indicated by symptoms

Important Distinctions:

• Subclinical hyperthyroidism is defined as TSH below 0.45 mIU/L with normal free T4 and T3 1, 2

  • Mild: TSH 0.1-0.45 mIU/L
  • More significant: TSH <0.1 mIU/L

• Overt hyperthyroidism is defined by low/undetectable TSH (<0.1 mIU/L) with elevated T4 or T3 1

Interpretation Caveats

While this TSH value is normal, it's important to note:

1. Single measurement limitation: TSH can vary by up to 50% day-to-day; a single value should not be overinterpreted 2

2. Non-thyroidal influences: TSH can be affected by:

   • Acute illness
   • Certain medications
   • Pregnancy
   • Adrenal insufficiency
   • Pituitary disorders 2

3. Clinical correlation: Laboratory values should always be interpreted in the context of the patient's clinical presentation 2

Recommendations

For a TSH value of 0.789 mIU/L:

• No treatment is indicated as this represents normal thyroid function 1, 2
• No additional thyroid testing is needed unless clinically indicated 2
• Routine monitoring is not necessary for asymptomatic individuals with normal TSH 1

Common Pitfalls to Avoid

1. Overdiagnosis: Labeling someone with thyroid disease based on borderline or single abnormal values can lead to unnecessary psychological distress and treatment 2

2. Overtreatment: Treating individuals with TSH values in the normal range can lead to iatrogenic hyperthyroidism with risks of osteoporotic fractures and atrial fibrillation 2

3. Ignoring clinical context: Laboratory values should always be interpreted alongside clinical findings 2

In summary, a TSH of 0.789 mIU/L represents normal thyroid function, and in the absence of symptoms or other clinical concerns, no further action is required.