Some patients with hypothyroidism can be challenging to treat and require special consideration. Use this section to review the cases of Steve, Jennifer, and Diana to see how to effectively manage their hypothyroidism with Synthroid (levothyroxine sodium).
*Hypothetical patient profile.
Steve is a 50-year-old man with hypothyroidism.
Past Medical History:
- 4 months ago, 190-lb patient presented with weight gain of 20 pounds in 1 year. Patient complained of fatigue, dry skin, constipation, cold intolerance, TSH 10.2 mIU/L, BP 150/60, total cholesterol 235 mg/dL; patient was diagnosed with hypothyroidism and started on Synthroid 137 mcg
- 8 weeks later, patient’s complaints continued. TSH 4.6 mIU/L; Synthroid dose increased to 150 mcg
Current Complaint:
- Nervousness, agitation, palpitations, and feeling hot for the past few months
Current Medications:
- Synthroid 150 mcg
Notable Physical Exam and Lab Findings:
- Sweating profusely despite air-conditioned exam room
- TSH 0.3 mIU/L
Diagnosis:
- Patient is displaying symptoms of being overreplaced with current dose of Synthroid of 150 mcg; TSH test confirmed
Treatment Plan Considerations:
- Decrease dose of Synthroid
- Recheck TSH levels in 4-6 weeks
- Managing hypothyroidism requires frequent monitoring
- Study of more than 1500 patients found that 40% of patients being treated for hypothyroidism were not within the normal therapeutic TSH range15
COLORADO THYROID DISEASE PREVALENCE STUDY15
(N=1525)
Therapeutic TSH range: 0.3-5.1 mIU/L
†Euthyroid = normal thyroid function.
Achieving steady TSH levels and hormonal stability requires precise, individualized dosing, and adequate monitoring is essential in stabilizing TSH levels.2
- Under- or overmedicating can have serious effects2
- With a narrow therapeutic range, even small dose changes in levothyroxine, including Synthroid, can affect TSH levels2
THE CARR STUDY: PROOF THAT PRECISE DOSING MATTERS16
Adapted from a 1988 biochemical study conducted in 21 adult Caucasian patients in the United Kingdom with primary hypothyroidism who were tested on a series of different thyroxine dosages to evaluate effectiveness of measuring TSH levels to monitor thyroid function.16
Following a 25-mcg dose change of levothyroxine, most patients had changes in TSH levels.
Jennifer is a 32-year-old woman in her first trimester of pregnancy with hypothyroidism that is managed on Synthroid.
Past Medical History:
- Diagnosed with hypothyroidism 3 years ago
- Started and managed on 50 mcg Synthroid
- Weight fluctuation
- Appendectomy
Current Complaint:
- Fatigue and facial puffiness
Current Medications:
- Synthroid 50 mcg
Notable Physical Exam and Lab Findings:
- Young woman with cold, dry skin and facial puffiness
- TSH 6.2 mIU/L
Diagnosis:
- Patient is displaying symptoms of hypothyroidism due to subtherapeutic dosing of Synthroid; TSH test confirmed
Treatment Plan Considerations:
- Increase dose of Synthroid
- Recheck TSH levels in 4 weeks
TSH levels may increase during pregnancy. TSH should be monitored and Synthroid dosage adjusted during pregnancy.
- 2017 ATA Guidelines state that:
- Between 50% and 80% of treated hypothyroid women need to increase their levothyroxine dosing during pregnancy18
Diana is a 70-year-old woman who has a history of hypothyroidism that has been managed on 112 mcg of Synthroid for the past 5 years.
Past Medical History:
- Hypothyroidism diagnosed 10 years ago
- Gastroesophageal reflux disease (GERD) diagnosed 6 months ago
- Enlarged thyroid
Current Complaint:
- Increasing hair loss, fatigue, chronic constipation for the past few months
Current Medications:
- Synthroid 112 mcg
- Daily fiber supplements
- Proton pump inhibitor (PPI)
Notable Physical Exam and Lab Findings:
- Well-nourished elderly woman with thinning hair
- TSH 5.7 mIU/L
Diagnosis:
- Patient is displaying symptoms of hypothyroidism (TSH test confirmed), most likely due to the initiation of a PPI and the concurrent use of daily fiber supplements
Treatment Plan Considerations:
- Counseled patient to take Synthroid on an empty stomach and at least 4 hours before or after other medications
- Recheck TSH levels in 6-8 weeks
- Certain medications, supplements, and foods can affect absorption of levothyroxine, including Synthroid
- Gastric acidity is essential for adequate absorption of levothyroxine; therefore, administration of a proton pump inhibitor may affect the intragastric pH, which can reduce absorption2
- Levothyroxine should be taken on an empty stomach and at least 4 hours before or after medications known to interfere with absorption2
- Dietary fiber may bind and decrease the absorption of levothyroxine from the gastrointestinal tract2
- The Third National Health and Nutrition Examination Survey (NHANES III) data have shown that the rate of elevated TSH (>4.5 mIU/L) increased with age19
