From the FDA Drug Label
The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal intellectual and physical growth and development. In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age Serum T4 and TSH levels should then be obtained. If the T4 is low and the TSH high, the diagnosis of permanent hypothyroidism is established, and levothyroxine therapy should be reinstituted. The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature During pregnancy, serum T4 levels may decrease and serum TSH levels increase to values outside the normal range Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking Levothyroxine Sodium Tablets, USP should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of Levothyroxine Sodium Tablets, USP A serum TSH level should be obtained 6-8 weeks postpartum
Synthroid (levothyroxine) Treatment for Hypothyroidism:
- The goal of treatment is to achieve and maintain normal intellectual and physical growth and development.
- Treatment involves administering levothyroxine to replace the missing thyroid hormones.
- Target TSH and T4 Levels:
- Before treatment: low T4 and high TSH levels indicate hypothyroidism.
- During treatment: TSH and T4 levels should be monitored regularly to avoid undertreatment or overtreatment.
- After treatment: TSH and T4 levels should be within normal range, indicating effective treatment.
- Monitoring:
- Serum T4 and TSH levels should be obtained regularly to monitor treatment efficacy.
- Patients should be monitored closely to avoid undertreatment or overtreatment.
- Special Considerations:
- Pregnancy: TSH levels should be measured during each trimester, and the dose of levothyroxine should be adjusted as needed.
- Pediatric Patients: Treatment should be initiated immediately upon diagnosis, and patients should be monitored closely to avoid undertreatment or overtreatment.
- Geriatric Patients: Levothyroxine therapy should not be initiated at the full replacement dose due to the increased prevalence of cardiovascular disease among the elderly 1.
- Indications and Usage: Levothyroxine sodium is used for the treatment of hypothyroidism, including primary, secondary, and tertiary hypothyroidism, and subclinical hypothyroidism 1.
From the Research
Synthroid (levothyroxine) is the standard treatment for hypothyroidism, and its use should be guided by the most recent and highest quality evidence to optimize patient outcomes in terms of morbidity, mortality, and quality of life. According to the most recent study 2, hypothyroidism is a common condition worldwide that affects almost all body systems and has a wide variety of clinical presentations. The diagnosis is typically made on biochemical grounds through serum thyroid function tests, with reference ranges based on fixed percentiles of the population distribution.
Treatment Initiation and Monitoring
Before treatment, patients with primary hypothyroidism typically have elevated TSH levels (often above 10 mIU/L) and low free T4 levels (below the reference range of approximately 0.8-1.8 ng/dL) 2. Treatment begins with a standard dose of 1.6 mcg/kg/day for most adults, though elderly patients or those with cardiac conditions may start at lower doses (25-50 mcg/day). During treatment, TSH and free T4 levels are monitored every 6-8 weeks initially, with dose adjustments made in 12.5-25 mcg increments until optimal levels are achieved.
Target TSH and Free T4 Levels
The target TSH for most adults is 0.5-2.5 mIU/L, with free T4 in the mid to upper half of the normal range 2. For elderly patients or those with cardiac disease, a slightly higher TSH target of 1-4 mIU/L may be appropriate. Once stabilized, monitoring can decrease to every 6-12 months.
Administration and Potential Interactions
Levothyroxine should be taken consistently, on an empty stomach, 30-60 minutes before breakfast or 3-4 hours after the last meal of the day, and separated from medications or supplements that can interfere with absorption (like calcium, iron, or antacids) 3.
Effectiveness and Ongoing Considerations
The effectiveness of treatment is based primarily on normalization of TSH levels, which indicates that the body is receiving adequate thyroid hormone replacement 2. However, some patients may experience persistent symptoms despite normal thyroid function tests, leading to debates around treatment thresholds and strategies. The use of liothyronine or desiccated thyroid extract has been explored in some cases, but levothyroxine monotherapy remains the standard treatment for hypothyroidism due to its safety, efficacy, and cost-effectiveness 2.
Key points to consider in the management of hypothyroidism include:
- The importance of individualized reference intervals for thyroid function tests based on factors like age, sex, and special circumstances such as pregnancy.
- The need for ongoing monitoring and potential dose adjustments to maintain optimal TSH and free T4 levels.
- The consideration of combination therapy with triiodothyronine (T3) for patients who do not respond adequately to levothyroxine monotherapy, although the evidence for this approach is still evolving 4.