@fmwentworth My thyroid levels were all on the low side of normal after 6 years with long COVID and adding in a supplement of thyroid made me feel much better. Here is what low T3 does to you:

Low T3 symptoms primarily include fatigue and weakness, weight gain, and cold intolerance, often developing gradually. Other common signs involve brain fog (trouble concentrating or memory lapses), dry skin and hair loss, muscle aches and joint pain, and a slowed heart rate.

Additional symptoms associated with low T3 levels include:
Constipation and difficulty losing weight despite diet and exercise.
Depression, anxiety, and mood disturbances.
Irregular or heavy periods and fertility issues in women.
Weakened immunity leading to higher susceptibility to infections.
Metabolic slowdown resulting in high cholesterol and insulin resistance.