From the FDA Drug Label
The general aim of therapy is to normalize the serum TSH level TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of levothyroxine sodium therapy and/or of the serum TSH to decrease below 20 IU per litre within 4 weeks may indicate the patient is not receiving adequate therapy
A significantly elevated TSH level of 109 and a low T4 level of 0.7 indicate that the patient is likely experiencing severe hypothyroidism. The patient's TSH level is above the normal range, and the T4 level is below the normal range, suggesting that the thyroid gland is not producing enough thyroid hormones. This combination of lab results may indicate that the patient is not receiving adequate thyroid hormone replacement therapy or that the patient has primary hypothyroidism that requires treatment 1.
- Key points:
- Elevated TSH level indicates hypothyroidism
- Low T4 level confirms hypothyroidism
- Patient may require adjustment of thyroid hormone replacement therapy
- Close monitoring of TSH and T4 levels is necessary to assess the adequacy of therapy 1
From the Research
A significantly elevated Thyroid-Stimulating Hormone (TSH) level of 109, combined with a low Thyroxine (T4) level of 0.7, indicates primary hypothyroidism, a condition where your thyroid gland is underactive and not producing enough thyroid hormone. The standard treatment for this condition is levothyroxine (synthetic T4), which is typically started at a dose of 1.6 micrograms per kilogram of body weight daily, taken on an empty stomach 30-60 minutes before breakfast or at bedtime, at least 4 hours after any medications that might interfere with absorption, as suggested by 2.
Key Considerations
- The initial dose may be lower (25-50 micrograms) for elderly patients or those with heart disease.
- Your doctor will monitor your TSH levels every 6-8 weeks initially and adjust your dose accordingly, with the goal of normalizing TSH (typically 0.4-4.0 mIU/L), as indicated by 3.
- Levothyroxine is usually a lifelong medication.
- This condition occurs because your thyroid gland cannot produce sufficient hormone despite stimulation from the pituitary gland, which increases TSH production in an attempt to boost thyroid function.
- Common causes include Hashimoto's thyroiditis (an autoimmune condition), iodine deficiency, or previous thyroid surgery or radiation treatment.
Treatment Approach
- According to 4, the decision to treat subclinical hypothyroidism should be individualized, taking into account risks and beneficial outcomes of levothyroxine therapy.
- As noted in 5, normal T3 levels can be achieved with traditional levothyroxine therapy alone in patients who have undergone near-total or total thyroidectomy, suggesting that T3 administration is not necessary to maintain serum T3 values at their endogenous prethyroidectomy levels.
Monitoring and Adjustment
- Regular monitoring of TSH levels is crucial to adjust the levothyroxine dose and ensure that the patient's thyroid hormone levels are within the normal range, as emphasized by 2.
- The goal of treatment is to normalize TSH levels and alleviate symptoms of hypothyroidism, while minimizing the risk of adverse effects, such as osteoporotic fractures and atrial fibrillation, especially in the elderly, as highlighted by 2.