Effect of Levothyroxine on Cardiac Function and Structure in Subclinical Hypothyroidism: A Double Blind, Placebo-Controlled Study
Subclinical hypothyroidism (sHT) affects 5–15% of the general population; however, the need of lifelong l-T4 therapy is still controversial. As myocardium is a main target of thyroid hormone action, we investigated whether sHT induces cardiovascular alterations. Twenty sHT patients were randomly ass...
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Veröffentlicht in: | The journal of clinical endocrinology and metabolism 2001-03, Vol.86 (3), p.1110-1115 |
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Sprache: | eng |
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Zusammenfassung: | Subclinical hypothyroidism (sHT) affects 5–15% of the general
population; however, the need of lifelong l-T4
therapy is still controversial. As myocardium is a main target of
thyroid hormone action, we investigated whether sHT induces
cardiovascular alterations. Twenty sHT patients were randomly assigned
to receive placebo or l-T4 therapy and were
followed for 1 yr. Twenty sex- and age-matched normal subjects served
as controls. Doppler echocardiography and videodensitometric analysis
were performed in all subjects. Myocardium textural parameters were
obtained as mean gray levels, which were then used to calculate the
cyclic variation index (CVI; percent systolic/diastolic change in mean
gray levels).
Patients had a significantly higher isovolumic relaxation time
(3.1 ± 0.5 vs. 2.6 ± 0.6;
P < 0.03), peak A (0.77 ± 0.16
vs. 0.56 ± 0.13 m/s; P <
0.01), and preejection/ejection time (PEP/ET) ratio (0.72 ± 0.05
vs. 0.57 ± 0.06; P < 0.03)
and a lower CVI (P < 0.0001) than controls. CVI
was inversely related to TSH level (P < 0.0001)
and PEP/ET ratio (P < 0.01).
l-T4-treated patients showed a significant
reduction of the PEP/ET ratio (P < 0.05), peak A
(P < 0.05), and isovolumic relaxation time
(P < 0.05) along with a normalization of CVI.
Conversely, no changes were observed in the placebo-treated group.
In conclusion, sHT affects both myocardial structure and contractility.
These alterations may be reversed by l-T4
therapy. |
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ISSN: | 0021-972X 1945-7197 |
DOI: | 10.1210/jcem.86.3.7291 |