Thyroid Function in Winter: 
Inputs from Dr Om Lakhani 
@omlakhani
Seasonal variations in thyroid function, particularly during winter months?

Key take aways

1. Seasonal TSH Variations:

TSH levels tend to rise during winter, peaking in January, with a more pronounced effect in individuals with subclinical hypothyroidism.

2. Thyroid Hormone Patterns:

Free T3 (FT3): Levels decrease in winter, inversely related to TSH.

Free T4 (FT4): Remains relatively stable with minor variations.

In hypothyroid patients on levothyroxine, both T3 and FT4 levels are lower in winter.

3. Mechanisms Behind Winter Thyroid Changes:

Physiological Adaptations: Increased metabolic demands and circadian disruptions (altered melatonin and deiodinase activity).

Environmental Factors: Reduced vitamin D levels and shorter daylight hours affect thyroid function and metabolism.

4. Clinical Implications:

Monitoring: Regular TSH, FT4, and FT3 monitoring during winter, especially in subclinical hypothyroidism and regions with extreme seasonal variations.

Therapeutic Adjustments:

Small levothyroxine dose increases may be needed for elevated TSH and worsening symptoms.

Some patients might benefit from T3 supplementation or switching levothyroxine brands.

Supportive Measures:

Vitamin D supplementation in deficient patients.

Screening and managing Seasonal Affective Disorder (SAD).

Encouraging regular exercise and adequate sleep.

Conclusion:

Winter poses unique challenges to thyroid hormone homeostasis, necessitating a proactive approach in monitoring and managing hypothyroid patients. While routine seasonal dose adjustments require further research, awareness of these variations is crucial for optimal patient care.
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# Does the TSH increase in Winters ? Thyroid Function in Winter: A Mini-Review