What are the best vitamins to take for increasing thyroid?

iodine tablets

The thyroid hormone molecule hasTyrosine (an amino acid which you can buy OTC) at the centre with 4 iodine atoms hanging off that. A shorthand for this arrangement is T4. You can think of T4 more as your body's reservoir of thyroid hormone. If treated, this is what you are given, usually in a synthetic form.

When it's needed, the body then knocks an iodine off to make T3, which is the really active form. The enzyme that does this neat trick needs Selenium, and is poisoned by Mercury.

You say you want something natural. Did you know that there is a natural thyroid supplement, called Armour Thyroid? It contains T4 and T3, in the human body's required ratio of about 4 to 1. It's made in a standardised form from desiccated pig thyroid gland. Don't be alarmed! It's available on prescription in the US. I am in the UK and get a prescription for it, but I have to send that to a particular pharmacist who imports it from the US. But it was a long journey to get outside the usual box of synthetic hormone replacement. Try the website in sources below for information. If your husband has tested low and a doctor is convinced he needs hormone replacement, but you would rather do natural things, he may be lower than mere supplements can reach. I have to say that although I tried all these things, and in theory they should work, since they meet the body's need for thyroid building blocks, I was still not well enough and needed the actual hormone. But everyone is different.

So you could try Tyrosine (say 500mg/day), Iodine (you can take too much iodine - be careful. Kelp is a good source of natural iodine, to give you say 150micrograms iodine per day, I think), Selenium (say 200 micrograms per day) and keep your teeth free of mercury fillings if you can, and try to avoid contaminated fish (while still having enough omega3 oils of course!).

Read any labels carefully regarding dose. I checked my supplies for all but the Kelp, which is not in the cupboard for some reason, but I think it's 150micrograms

This information is not intended to diagnose or treat any condition. You should always consult a qualified physician. Unfortunately I have to say that! This is a contentious subject.
There are herbs that help too, but off the top of my head I can't remember them.
Good luck