Can you have an underactive thyroid with normal TSH?

[Ippodrom47]

Basically, that's what I have now and have had for quite a while. My T4 levels are at the low range or below, yet my TSH is never above 1-2. I have all common symptoms of hypothyroidism, I react negatively to beta carotene and supplemental iodine (which might have caused the issue in the first place). I also developed thyroid nodules over one year of the increased iodine intake. Why my TSH remain so low? Can it be due to goitrogens (I used to eat lots of raw bok choy cabbage and other cruciferous vegetables along with peanuts some time ago). I need my thyroid to be active! :) Thanks!

 

[ALS]

Get a thyroid panel with an antibody (TPO) test included. I've got Hashimoto's and my TSH is close to 1 now. Still can't lose weight.

 

[AgentCranberry]

Yes, that is possible.
Very basic explanation: The TSH is your brain's signal to the thyroid gland how much thyroid hormones it should produce regulated by a feedback mechanism. It depends on the proper function of the hypothalamus and the pituitary gland.

Two examples: 1. Destruction of the tissue of the thyroid gland without any other problems leads to high TSH and low thyroid hormone (the feedback mechanism is intact but the gland cannot satisfy the demand)
2. Starvation leads to low to normal TSH and low thyroid hormones: The thyroid gland is intact but the hypothalamus "decides" to have less thyroid hormones

Edit: Iirc @Dan Wich from toxinless.com has a great and easy to follow video about that (it includes the peripheral conversion of T4 to T3 which many explanantions lack). I blocked youtube here but you should find either there or on his website.

Edit 2: Regarding your other questions: Did you have a full thyroid panel including antibodies? How is your lifestyle? What do you work? Do you train a lot? Do you have a history of undereating? Did you give birth? Did you have any head trauma? Do you get sunlight regularly? Are you vegan or vegetarian? What do you eat on a regular basis?
Past consumption of bok choy and peanuts would very likely not lead to permanent damage, I would not think about that.

 

[ALS]

View: https://www.youtube.com/watch?v=qEUl2mbEpi8

 

[rei]

Ray seems to think TSH over 1 means thyroid is not functioning well. In one pretty recent podcast the caller had 0.5 and he said they probably would benefit from thyroid.