Myxedema in Both Hyperthyroidism and Hypothyroidism: A Hormetic Response?

Area of Science:

• Endocrinology
• Thyroidology
• Body Fluid Physiology

Background:

• Myxedema is typically associated with severe hypothyroidism but can paradoxically manifest in hyperthyroidism.
• The underlying mechanism for myxedema in both hyperthyroid and hypothyroid states remains unclear.
• Thyroid hormones (THs) are known to exert hormetic effects, exhibiting biphasic responses depending on dose and duration.

Purpose of the Study:

• To investigate body fluid distribution in thyroid dysfunction using bioelectrical impedance analysis (BIA).
• To explore the potential role of hormesis in the development of myxedema in both hyperthyroidism and hypothyroidism.
• To assess the utility of BIA in evaluating fluid body composition across different thyroid functional statuses.

Main Methods:

• Analysis of body fluid distribution via bioelectrical impedance analysis (BIA).
• Study included 103 thyroid patients categorized by functional status (euthyroid, subclinical, overt hyperthyroidism, severe hypothyroidism).
• Comparison of BIA parameters between patient groups and euthyroid controls.

Main Results:

• BIA parameters were unaltered in subclinical thyroid dysfunctions compared to euthyroid controls.
• Significant alterations in BIA parameters were observed in overt hyperthyroidism and severe hypothyroidism.
• Fluid body composition changes were more pronounced in hyperthyroidism than in hypothyroidism, suggesting a hormetic response to THs.
• BIA is valuable for monitoring overt and severe thyroid dysfunctions but not subclinical ones.

Conclusions:

• Myxedema in both hypothyroidism and hyperthyroidism represents a hormetic-type response to thyroid hormones (THs).
• Bioelectrical impedance analysis (BIA) is a useful tool for assessing and monitoring body fluid composition in severe thyroid dysfunctions.
• BIA provides limited value for subclinical thyroid disease evaluation regarding fluid body composition.