Causal relationship between hypothyroidism and temporomandibular disorders: evidence from complementary genetic...

Area of Science:

• Endocrinology
• Genetics
• Oral Health

Background:

• Observational studies suggest a link between thyroid health and temporomandibular disorders (TMDs).
• Causality and specific thyroid conditions (hypothyroidism vs. hyperthyroidism) involved in TMDs remain unclear.

Purpose of the Study:

• To investigate the causal effects of thyroid conditions on TMDs using Mendelian randomization.
• To determine if hypothyroidism or hyperthyroidism specifically contributes to TMD development.

Main Methods:

• Mendelian randomization (MR) employed genetic variants for thyrotropin (TSH), free thyroxine (fT4), hypothyroidism, hyperthyroidism, and TMDs.
• Inverse-variance weighted (IVW), weighted median, and MR-Egger methods used for univariable and multivariable analyses.
• Sensitivity analyses conducted to assess pleiotropy and heterogeneity.

Main Results:

• Hypothyroidism showed a significant causal effect on increased TMD risk (IVW OR: 1.12, p=0.001).
• No significant causal associations found for hyperthyroidism, TSH, or fT4 with TMDs.
• Multivariable MR confirmed hypothyroidism's independent effect on TMDs (OR: 1.10, p=0.006).

Conclusions:

• Hypothyroidism may directly increase TMD risk, underscoring the importance of thyroid health management for TMD prevention.
• Clinicians should consider hypothyroidism in patients presenting with temporomandibular discomfort.
• Potential confounders, pleiotropy, and selection bias warrant caution in interpreting MR findings.