I thought that my thyroid would be a problem; since my hands and feet are always cold. My core is really warm; especially during sleep when my metabolism is well relaxed. But my body temp is generally low; and my basal temp average is low. Nothing else about me is normal for the general public; so I'm not sure about these averages.
I did try thyroid glandular many years ago. Like you, I don't trust what the glandulars do after long term use. I just wanted to see if it helped my thyroid. It did not help. Then I tried Iodine megadose for 5 months. No help there either.
I think I will stick with nettle, seaweed, ashwagandha, and any other herbs that help the endocrine system.
But I'm more convinced that it is started by the adrenals.