Revisiting an old thread:

My mother always had very low thyroid function, and offspring of a genetically hypothyroid parent reportedly have a 50% chance of inheriting the same condition. My resting pulse of 43bpm has always been lower than I deserve for my good, but not elite, level of fitness, and my body temperature has generally hovered a few tenths below the textbook normal of 37.0C. I recently recovered from the flu, my first major illness in 15 years, and now I sometimes have basal oral temperature readings as low as 35.2C = 95.4F. I have become much more sensitive to cold than before, and my hands feel even colder than usual to my wife. I also realized that I had run out of kelp tablets, which I have taken daily for many years. My athletic and mental performance have been a little sub-par, which I had attributed to age.

I restarted my kelp supplements today and added an herbal thyroid support pill, and I shall track my symptoms over the coming weeks. If I am still having trouble, I'll need to get checked for autoimmune problems.