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Evaluation and follow-up of clinically euthyroid children with normal free T4 and suppressed TSH
Priya Vaidyanathan1, Paul B Kaplowitz
1Department of Endocrinology, Children's National Medical Center, Washington, DC, USA. pvaidyan@cnmc.org
Insights
Severely suppressed TSH (< 0.1 mIU/L) with normal free T4 is uncommon. Most patients resolve spontaneously, but some develop hypothyroidism or hyperthyroidism, warranting careful monitoring.
Area of Science:
- Pediatric Endocrinology
- Thyroidology
- Internal Medicine
Background:
- Subnormal thyroid-stimulating hormone (TSH) levels between 0.1-0.4 mIU/L are common and benign.
- TSH suppression to < 0.1 mIU/L with normal free thyroxine (T4) is less common and potentially concerning.
Purpose of the Study:
- To review cases of suppressed TSH with normal free T4.
- To summarize patient features and outcomes for better clinical management.
Main Methods:
- Retrospective chart review of 23 pediatric patients with TSH < 0.1 mIU/L and free T4 0.8-2 ng/dl.
- Analysis of historical, clinical, and laboratory data, with outcome assessment.
Main Results:
- 61% of patients normalized TSH spontaneously within 3.7 months.
- 17% developed hypothyroidism, and 9% progressed to overt hyperthyroidism.
- 13% had persistent TSH suppression; 54.5% of tested patients had elevated thyroid peroxidase antibodies (TPO).
Conclusions:
- Overt hyperthyroidism occurred in only 2/23 patients.
- Transient TSH suppression is common and often resolves spontaneously.
- Monitoring is recommended for symptomatic patients or those with persistent suppression.
Aim:
Although subnormal TSH between 0.1-0.4 mIU/L is fairly common and benign, suppression of TSH to < 0.1 mIU/L with normal free T4 is less common and more worrisome. We have conducted a retrospective chart review of a collection of such cases and have summarized the features and outcome on follow up.
Methods:
We studied 23 consecutive patients referred from 2005-07 to our pediatric endocrine clinic with TSH < 0.1 mIU/L and free T4 in the range of 0.8-2 ng/dl. We collected historical, clinical and laboratory data, and analyzed their outcome.
Results:
The natural evolutions of these subjects were separated into 4 groups. Group 1, 14 subjects, (61%) became euthyroid within a mean of 3.7 months. Group 2, 4 subjects, (17%) became hypothyroid within a mean of 2.8 months. Group 3, 2 subjects (9%) progressed to overt hyperthyroidism. Group 4, 3 subjects (13%) had persistently suppressed TSH, 8-14 months after initial testing, of which one had a multinodular goiter and had a thyroidectomy. Elevated thyroid peroxidase antibody (TPO) was seen in 54.5% of those tested.
Conclusion:
Only 2/23 in our series became overtly hyperthyroid. Substantial number of subjects had a short period of transient TSH suppression that resolved spontaneously. Markers suggestive of autoimmune thyroid disease were consistently seen in group 2 and less so in others. It is prudent to observe such cases in the short term with serial follow up TSH, free T4 and T3, and to reserve further testing and treatment for those who become symptomatic or do not resolve.
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