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Abstract
Background: The management of subclinical hypothyroidism (SH) is still controversial, as the benefit to risk ratio of prolonged l-thyroxine therapy is not clear cut. Some authors have shown abnormalities of myocardial function and structure in adults with SH, which could be reversed by l-thyroxine therapy. As SH frequently affects children with Down’s syndrome (DS), and almost one half of these are affected by congenital heart disease, a concomitant SH related impairment of cardiac function might further compromise their clinical condition.
Aims: To establish whether SH influences myocardial structure and function in children with DS.
Methods: Sixteen children with DS and untreated SH and 25 matched euthyroid controls with DS underwent echocardiographic analysis of left ventricular mechanics and tissue characterisation.
Results: None of the 16 patients had myocardial impairment.
Conclusion: Results suggest that children with DS who have SH are not at risk of cardiac disease. Clinicians should consider these data in the management of SH, as the benefit to risk ratio of prolonged l-thyroxine therapy is not clear cut.
- Down syndrome
- subclinical hypothyroidism
- TSH
- cardiac function
- A, peak of mitral flow velocity at end-diastole
- Aa, peak of mitral annular velocity at end-diastole
- AbTg, antithyroglobulin antibodies
- AbTPO, antiperoxidase antibodies
- BSA, body surface area
- CVIVS, cyclic variation at interventricular septum
- CVPW, cyclic variation at left ventricular posterior wall
- DS, Down’s syndrome
- DT, deceleration time
- DTI, Doppler tissue imaging
- E, peak of mitral flow velocity at the beginning of diastole
- Ea, peak of mitral annular velocity at the beginning of diastole
- FS, fractional shortening [(end-diastolic dimension − end-systolic dimension)/end-diastolic dimension]
- HR, heart rate
- IB, integrated backscatter
- INTIVS, averaged intensity at interventricular septum
- INTPW, averaged intensity at left ventricular posterior wall
- IVRT, isovolumic relaxation time
- IVS, interventricular septum
- IVSd, end-diastolic interventricular septum thickness
- LV, left ventricular
- LVEDd, left ventricular end-diastolic diameter
- LVMI, left ventricular mass index
- PW, posterior wall
- PWd, end-diastolic posterior wall thickness
- SH, subclinical hypothyroidism
- SVI, stress velocity indexσes, end-systolic meridional wall stress
- T3, triiodothyronine
- T4, thyroxine
- TSH, thyroid stimulating hormone
- VCFc, rate corrected velocity of circumferential fibre shortening