A Study of Thyroxine-Binding Globulin(TBG) Deficiency with Congenital Hypothyroidism
Presentation Number: SAT-0554
Date of Presentation: June 21st, 2014
Yong Hee Hong*1, Dong Hwan Lee2 and Sun Hee Lee3
1Soonchunhyang University Hospital, Bucheon, Korea, Republic of (South), 2College of Medicine, Soonchunhyang University, Seoul, Korea, Republic of (South), 3Graduate School of Medicine, Gacheon University of Medicine and Science, Gil Medical Center, Incheon, Korea, Republic of (South)
Introduction : Thyroxine-binding globulin (TBG) deficiency is known as a nonharmful condition transmitted as an X-linked trait. But TBG deficiency may lead to hypothyroidism requiring hormone supplementation very rarely. The suggested mechanisms are impaired transport, extrathyroidal storage of thyroid hormone and abnormal hypothalamus-pituitary axis response caused by fluctuation of free T4 level.
Patients and Methods : Data of 33 patients with TBG deficiency were studied from 1997 until 2011 in Pediatric Endocrinology Department of Soonchunhyang University Hospital. All patients were evaluated for thyroid function and TBG levels. In cases of TBG deficiency with hypothyroidism, after L-thyroxine supplementation during 3 years, discontinuing L-thyroxine treatment for 4 weeks, laboratory evaluation were performed again. Complete TBG deficiency was defined as <0.03 mg/L, partial TBG deficiency was defined as below 50% of normal range for age.
Results : All 33 patients had partial TBG deficiency. 19 patients had abnormal thyroid function requiring L-thyroxine supplementation. Initial mean TSH level was 9.4±6.1 uIU/mL in hypothyroid patients with partial TBG deficiency, 3.4±1.5 uIU/mL in euthyroid patients with partial TBG deficiency. Initial mean Free T4 level was 1.6±1.1 uIU/mL in hypothyroid patients with partial TBG deficiency, 2.7±1.0 uIU/mL in euthyroid patients with partial TBG deficiency. There were statistically differences in initial TSH and Free T4 levels between 2 patients group(P value = 0.004, 0.005). TBG level was decreased by 24.4±13.4 % compared with normal range for age in hypothyroid patients with partial TBG deficiency and 39.1±13.7 % in euthyroid patients with partial TBG deficiency. There were statistically differences between 2 patients group(P value = 0.039). 3 patients with hypothyroidism and partial TBG deficiency were transient, but 16 patients were permanent hypothyroidism after their 3 year old age.
Conclusion : Although very rare, TBG deficiency can cause hypothyroidism requiring L-thyroxine supplementation, even in partial TBG deficiency. We should carefully follow up thyroid function in TBG deficiency patients.
Nothing to Disclose: YHH, DHL, SHL