Bone health in children with long–term idiopathic subclinical hypothyroidism

Raffaella Di Mase,Mariacarolina Salerno,Francesca Santamaria,Andrea Esposito,Ciro Mainolfi,Manuela Cerbone,Claudio Pignata,Nicola Improda,Donatella Capalbo

doi:10.1186/1824-7288-38-56

Raffaella Di Mase, Mariacarolina Salerno + Show 7 more

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https://doi.org/10.1186/1824-7288-38-56

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Abstract

BackgroundSubclinical hypothyroidism (SH) is a relatively common condition characterized by a mild persistent thyroid failure. The management of children with SH is still a controversial issue and the decision to treat with L-thyroxine represents a clinical dilemma. Thyroid hormone and TSH play an important role in skeletal growth and bone mineral homeostasis.AimTo evaluate whether untreated idiopathic SH may affect bone health in childhood and to compare two different diagnostic tools such as dual-energy X-ray densitometry (DXA) and quantitative ultrasound (QUS).Patients and MethodsTwenty-five children and adolescents (11 males) aged 9.8 ± 3.5 years (range 4.2-18.7) with untreated idiopathic SH were enrolled in the study. SH was diagnosed on the basis of normal FT4 levels with TSH concentrations between 4.2 and 10 mU/l. Children have been followed for 3.3 ± 0.3 years from the time of SH diagnosis. Twenty-five healthy children, age- and sex-matched, were enrolled as controls. Patients and controls underwent DXA to evaluate lumbar spine bone mineral density (BMD) and QUS at proximal phalanges of the non-dominant hand to assess bone quality, measured as amplitude-dependent speed of sound (Ad-SoS) and bone transmission time (BTT).ResultsMean BMD Z-score was −0.4 ± 1.36 in patients and −0.2 ± 1.2 in controls. Mean Ad-SoS Z-score was 0.01 ± 1.0 in patients and 0.1 ± 1.2 in controls and mean BTT Z-score was −0.03 ± 0.8 and 0.04 ± 1.1 respectively. All values were within the normal range, both in patients and in controls. There were no statistically significant differences between the two groups.ConclusionBone health, evaluated by lumbar spine DXA and phalangeal QUS, is not impaired in our children, despite long-term duration of idiopathic SH. Data about bone status provided by QUS are comparable to those provided by DXA. Therefore, QUS may represent a good, cheaper and safe screening test for bone evaluation in children with SH.

Highlights

Subclinical hypothyroidism (SH) is a relatively common condition characterized by a mild persistent thyroid failure
Data about bone status provided by quantitative ultrasound (QUS) are comparable to those provided by Dual-energy X-ray densitometry (DXA)
Heterozygous TSH receptor (TSHR)+/− mice, despite normal T4 levels have significant decrease in bone density. This finding suggests that a mild increase in TSH levels may influence bone metabolism, in non-autoimmune subclinical hypothyroidism that may be related to inactivating mutation of TSHR

Summary

Introduction

Subclinical hypothyroidism (SH) is a relatively common condition characterized by a mild persistent thyroid failure. As for the effect of hypothyroidism on bone, hystomorphometry data indicated that hypothyroidism significantly prolongs the bone remodeling cycle resulting in a reduced bone turnover and a gain in bone mass and mineralization with consequent significantly greater thickness in cortical bone [17] In keeping with this data, several studies have reported on an increased BMD in adults with high or high-normal TSH, along with a positive correlation between BMD and TSH levels [18,19,20]. Heterozygous TSHR+/− mice, despite normal T4 levels have significant decrease in bone density This finding suggests that a mild increase in TSH levels may influence bone metabolism, in non-autoimmune subclinical hypothyroidism that may be related to inactivating mutation of TSHR. Measurement of bone mineral status in childhood and adolescence may help identifying subjects, who may be exposed to an increased risk of osteoporosis later in adulthood

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