This study supports and confirms the need for monitoring the side-effects of IM treatment on growth, bone density and vitamin D status in pediatric CML. Prolonged IM treatment was associated with low BMD without disturbing bone parameters. There was high prevalence of vitamin D insufficiency. Therefore, the beneficial effect of vitamin D supplement should be explored with regard to the effects on height velocity and BMD in CML patients with vitamin D insufficiency.

Context The two major forms of circulating thyroid hormones (THs) are T3 and T4. T3 is regarded as the biologically active hormone because it binds to TH receptors (TRs) with greater affinity than T4. However, it is currently unclear what structural mechanisms underlie this difference in affinity. Objective Prompted by the identification of a novel M256T mutation in a resistance to TH (RTH)α patient, we investigated Met256 in TRα1 and the corresponding residue (Met310) in TRβ1, residues previously predicted by crystallographic studies in discrimination of T3 vs T4. Methods Clinical characterization of the RTHα patient and molecular studies (in silico protein modeling, radioligand binding, transactivation, and receptor–cofactor studies) were performed. Results Structural modeling of the TRα1-M256T mutant showed that distortion of the hydrophobic niche to accommodate the outer ring of ligand was more pronounced for T3 than T4, suggesting that this substitution has little impact on the affinity for T4. In agreement with the model, TRα1-M256T selectively reduced the affinity for T3. Also, unlike other naturally occurring TRα mutations, TRα1-M256T had a differential impact on T3- vs T4-dependent transcriptional activation. TRα1-M256A and TRβ1-M310T mutants exhibited similar discordance for T3 vs T4. Conclusions Met256-TRα1/Met310-TRβ1 strongly potentiates the affinity of TRs for T3, thereby largely determining that T3 is the bioactive hormone rather than T4. These observations provide insight into the molecular basis for underlying the different affinity of TRs for T3 vs T4, delineating a fundamental principle of TH signaling.

Background The standard treatment of central precocious puberty (CPP) is gonadotropin-releasing hormone analogues (GnRHa). It is a concern that children treated with GnRHa are at risk of developing obesity which could impair the treatment outcomes. This study aimed to investigate the effect of GnRHa on body mass index (BMI) standard deviation score (SDS), and the influence of BMI status on treatment outcomes in children with idiopathic CPP (iCPP). Methods A retrospective cohort study in children with iCPP who completed GnRHa treatment and had attained near final adult height (NFAH) was conducted. Children with a history of disease or drug ingestion which could affect their BMI were excluded. BMI, BMI SDS, height (Ht), Ht SDS, predicted adult height (PAH), and NFAH were compared at baseline, 1 and 2 years during treatment, and at NFAH according to the baseline BMI status; normal weight and overweight/obesity. Results Fifty-eight children with iCPP treated with GnRHa were enrolled. The BMI SDS was significantly increased at 1 and 2 years during treatment in the overweight/obese group and at 1 year during treatment in the normal-weight group. However, at NFAH (2 years after treatment discontinuation), the BMI SDS was not statistically different from baseline in both groups. Ht gain, change in Ht SDS and BMI SDS were not statistically different from the baseline in both groups. Conclusions GnRHa results in a transient increase in BMI SDS during treatment and returned to baseline after treatment cessation. The benefit of GnRHa treatment on final Ht improvement is similar between overweight/obese and normal-weight patients.

Leu341 has been predicted from crystal structure as an important residue for thyroid hormone receptor (TR) β function, but this has never been confirmed in functional studies. Here, we describe a novel p.L341V mutation as a cause of resistance to thyroid hormone β, suggesting an important role for Leu341 in TRβ function. In silico and in vitro studies confirmed that substituting Leu341 with Val and other non-polar amino acids impairs sensitivity of TRβ for T3 with various degrees, depending on their side-chain size and orientation.