Background: Macro TSH is a high molecule weighed complex with low bioactivity that is comprised of TSH and anti-TSH antibodies. Potentiality of macro TSH should be kept in mind in clinically euthyroid and asymptomatic patients with normal free T4 and T3 levels and relatively high TSH levels. Diagnosis of macro TSH is suspected if polyethylene glycol (PEG) precipitable TSH exceeds %75 and confirmed if high molecule weighed TSH is shown with gel filtration chromotography (GFC). Here we represent a case with macro TSH who had initially been treated with levothyroxine for subclinical hypothyroidism.
Case Presentation: A 7 year old girl was admitted to hospital with high level of TSH detected in routine control. She did not have any complaints and her physical examination was normal. Serum levels of TSH was 19.6 μU/ml, free T4 (fT4) was 1.53 ng/dl and thyroid antibodies were negative. 1 mcg/kg per day of levothyroxine was initiated. In the follow up TSH levels could not be suppressed although levothyroxine dosage was raised to 1.5 mcg/kg per day and the dosage could not be raised more because she had feeling of discomfort when she took the drug. There was %86 TSH precipitation with PEG (meanwhile TSH: 39 μU/ml, fT4: 0.95 ng/dl). So the presence of macro TSH was suspected and levothyroxin treatment was stopped. At the end of seven months without treatment fT4 level was 0.73 ng/dl, TSH level was 17.3 μIU/ml and PEG precitable TSH was %99. Immuno globulin G bound TSH was %57.7 and more than %90 of TSH was eluted at 150 kDa in GFC which confirmed macro TSH diagnosis.
Conclusion: In subclinical hypothyroidism cases with TSH levels that are unexpectedly high and unresponsive to levothyroxine treatment, presence of macro TSH should be investigated to prevent unnecessary treatments.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology