With a thyroid‑stimulating hormone level of 9 mIU/L and normal free triiodothyronine and free thyroxine, am I euthyroid?

TSH of 9 mIU/L with Normal Free T3 and Free T4: Not Euthyroid

You are not euthyroid—you have subclinical hypothyroidism, which is a clinically significant condition that requires confirmation and likely treatment. 1

Definition and Diagnosis

• Subclinical hypothyroidism is defined as elevated TSH (>4.5 mIU/L) with normal free T4 and free T3 levels. 1, 2
• Your TSH of 9 mIU/L clearly exceeds the upper limit of the normal reference range (0.45-4.5 mIU/L), placing you in the subclinical hypothyroidism category. 1
• The term "euthyroid" means normal thyroid function with TSH in the reference range and normal thyroid hormones—your elevated TSH indicates your thyroid gland is struggling to maintain normal hormone levels. 1

Why This Matters Clinically

A TSH of 9 mIU/L carries significant clinical implications:

• You have approximately 2-5% annual risk of progressing to overt hypothyroidism (where free T4 would also become low). 1, 2
• This TSH level is associated with cardiac dysfunction, including delayed myocardial relaxation, reduced cardiac output, and increased systemic vascular resistance. 1
• You likely have an adverse lipid profile with elevated LDL cholesterol and triglycerides. 1

Confirmation Before Treatment

Before any treatment decision, you must confirm this is persistent:

• Repeat TSH and free T4 measurement after 3-6 weeks, because 30-60% of initially elevated TSH values normalize spontaneously. 1
• This confirmation step is critical—transient TSH elevations can occur during recovery from acute illness, after iodine exposure (like CT contrast), or due to certain medications. 1

Treatment Threshold and Recommendations

Your TSH of 9 mIU/L places you just below the threshold where treatment becomes strongly recommended:

• TSH >10 mIU/L: Levothyroxine therapy is recommended regardless of symptoms, due to the higher progression risk and cardiovascular effects. 1, 2
• TSH 4.5-10 mIU/L (your range): Treatment decisions should be individualized based on:
  • Symptoms (fatigue, weight gain, cold intolerance, constipation)—a 3-4 month trial of levothyroxine may be beneficial. 1
  • Anti-TPO antibodies—if positive, you have 4.3% annual progression risk vs 2.6% if negative, favoring treatment. 1, 2
  • Pregnancy or planning pregnancy—treatment is mandatory to prevent adverse outcomes. 1, 2
  • Goiter or infertility—these favor treatment. 2

Common Pitfall to Avoid

Do not assume you are "fine" because your free T3 and free T4 are normal. The elevated TSH indicates your pituitary is working overtime to stimulate your failing thyroid gland to produce adequate hormone—this compensated state may not last, and the TSH elevation itself has metabolic consequences. 1

Next Steps

1. Confirm with repeat testing in 3-6 weeks (TSH + free T4). 1
2. Measure anti-TPO antibodies to identify autoimmune thyroiditis and predict progression risk. 1
3. Assess for symptoms of hypothyroidism that may warrant treatment even at this TSH level. 1
4. If confirmed and symptomatic, or if anti-TPO positive, or if planning pregnancy—initiate levothyroxine therapy. 1, 2