What is the significance of elevated Thyroid-Stimulating Hormone (TSH) levels, specifically 55, in a patient taking Synthroid (levothyroxine) 175 micrograms daily?

From the Guidelines

A TSH level of 55 while taking Synthroid 175mcg daily indicates significant hypothyroidism and inadequate thyroid hormone replacement, and the dose likely needs to be increased to prevent long-term complications such as osteoporosis, fractures, and abnormal cardiac output. Normal TSH typically ranges between 0.4-4.0 mIU/L, and your level is substantially elevated. According to the U.S. Preventive Services Task Force recommendation statement 1, levothyroxine therapy is a synthetic preparation of a natural hormone found in the body, and treatment of hypothyroidism with levothyroxine generally lasts for many years. However, the previous review found that one quarter of patients who received levothyroxine were inadvertently maintained on doses high enough to make TSH levels undetectable, which could increase risk for osteoporosis, fractures, abnormal cardiac output, or ventricular hypertrophy.

Some possible factors that could explain this high TSH despite your current dose include:

• Poor medication absorption
• Taking Synthroid with food or certain medications (calcium, iron supplements, antacids)
• Missed doses
• Increased thyroid hormone requirements due to weight gain, pregnancy, or other medical conditions. Your provider may increase your Synthroid dose incrementally, possibly to 200mcg daily, and will want to recheck your thyroid levels in 6-8 weeks. Until you see your provider, continue taking your current dose as prescribed, take it on an empty stomach with water 30-60 minutes before eating, and separate it from other medications by at least 4 hours. Untreated hypothyroidism can lead to fatigue, weight gain, cold intolerance, and other health complications, so prompt medical attention is important, as noted in the study published in the Annals of Internal Medicine 1.

From the FDA Drug Label

The dosage of levothyroxine sodium tablets for hypothyroidism or pituitary TSH suppression depends on a variety of factors including: the patient's age, body weight, cardiovascular status, concomitant medical conditions (including pregnancy), concomitant medications, co-administered food and the specific nature of the condition being treated For adult patients with primary hypothyroidism, titrate until the patient is clinically euthyroid and the serum TSH returns to normal Table 1. Levothyroxine Sodium Tablets Dosing Guidelines for Hypothyroidism in Adults* *Dosages greater than 200 mcg/day are seldom required. An inadequate response to daily dosages greater than 300 mcg/day is rare and may indicate poor compliance, malabsorption, drug interactions, or a combination of these factors Patient Population Starting Dosage Dosage Titration Based on serum TSH or Free-T4 Adults diagnosed with hypothyroidism Full replacement dose is 1.6 mcg/kg/day. Some patients require a lower starting dose. Titrate dosage by 12. 5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid.

The patient is taking 175mcg of levothyroxine daily, and their TSH level is 55, which is higher than the normal range.

• The dosage may need to be adjusted based on the patient's serum TSH level.
• The patient's current dosage is within the range that may be required for some patients, but an inadequate response to daily dosages may indicate poor compliance, malabsorption, drug interactions, or a combination of these factors 2.
• It is recommended to titrate the dosage by 12.5 to 25 mcg increments every 4 to 6 weeks, as needed, until the patient is euthyroid.
• The patient should be monitored regularly to assess their clinical response and laboratory parameters.

From the Research

TSH Elevation on Synthroid

• A TSH level of 55 on Synthroid 175mcg daily indicates that the patient's hypothyroidism is not adequately controlled 3.
• The most common cause of persistent TSH elevation in patients on high-dose thyroid hormone replacement is poor patient compliance with their medication regimen 3.
• Other possible causes of TSH elevation in compliant patients include malabsorption of levothyroxine, which can be assessed using an absorption test 4.

Treatment Options

• For patients who remain symptomatic on levothyroxine (LT4) therapy, clinical guidelines recommend a trial of combination therapy with LT4 and liothyronine (LT3) 5, 6.
• The decision to start treatment with liothyronine should be a shared decision between the patient and clinician, taking into account the patient's individual needs and circumstances 6.
• In some cases, desiccated thyroid extract (DTE) may be considered as an alternative to levothyroxine monotherapy, although its use is not formally regulated by the FDA 5.

Monitoring and Adjustment

• Levothyroxine doses should be optimized to achieve a TSH level within the target range (0.3-2.0 mU/L) for 3 to 6 months before assessing the therapeutic response 6.
• In some patients, it may be acceptable to have a serum TSH level below the reference range (e.g., 0.1-0.3 mU/L), but not fully suppressed in the long term 6.
• Regular monitoring of TSH levels and clinical symptoms is necessary to adjust the treatment regimen as needed and ensure optimal control of hypothyroidism 3, 7.