Effects of Six Months of Levothyroxine Therapy on Sympathovagal Imbalance and Cardiometabolic Profile in Overt Hypothyroid Patients

TL;DR

This study finds that six months of levothyroxine therapy improves but does not fully restore autonomic and metabolic health in overt hypothyroid patients.

Contribution

The study provides new insights into the incomplete recovery of autonomic and metabolic profiles in overt hypothyroidism after six months of levothyroxine treatment.

Findings

Levothyroxine therapy improved parasympathetic modulation and partially restored sympathovagal balance.

Lipid profiles improved but did not reach levels seen in healthy controls.

Oxidative stress remained elevated and was linked to persistent autonomic dysfunction.

Abstract

Introduction: Hypothyroidism, a common endocrine disorder, is linked to cardiovascular risks arising from autonomic imbalance and metabolic dysregulation. While overt hypothyroidism (OH) manifests distinct thyroid hormone abnormalities, subclinical hypothyroidism (SCH) presents milder hormonal changes. Levothyroxine therapy is widely used for thyroid function restoration, but its long-term effects on autonomic and cardiovascular health in OH remain understudied. This study investigates the therapeutic effects of six months of levothyroxine treatment on autonomic function and metabolic parameters in OH patients.

Materials and methods: A follow-up study was conducted on OH patients receiving levothyroxine therapy. Participants with confounding cardiovascular comorbidities were excluded. Clinical assessments included autonomic function tests, metabolic profiling (lipid and thyroid parameters), and inflammatory/oxidative stress markers. Comparative analyses were performed against healthy controls.

Results: Levothyroxine therapy effectively restored thyroid hormone levels in OH patients. Autonomic function tests demonstrated improved parasympathetic modulation and partial sympathovagal balance recovery, though residual autonomic irregularities persisted. Lipid profiles showed marked improvement but did not fully normalize compared to controls. Inflammatory and oxidative stress markers decreased significantly post-therapy, yet remained elevated relative to healthy individuals. Statistical modeling identified oxidative stress as a key contributor to autonomic dysfunction.

Discussion: While levothyroxine normalized thyroid function and improved autonomic balance, incomplete resolution of metabolic and inflammatory abnormalities suggests persistent cardiovascular risks in OH patients after six months of therapy. The findings highlight the need for extended treatment durations to achieve comprehensive cardiovascular risk mitigation.

Conclusion: Despite therapeutic benefits, OH patients retain residual cardiovascular risks post-levothyroxine therapy, necessitating long-term monitoring. Future research should investigate optimal treatment durations and adjunct therapies to address persistent autonomic and metabolic dysfunction in this population.

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