I've never seen a thyroglobulin test before, and I don't have a solid understanding of how thyroid hormones are manufactured. So, I Googled and found this lovely site from Colorado State University.

http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/synthesis.html

I didn't have to go far down the page before I read this:

"1.Iodination of tyrosines on thyroglobulin (also known as 'organification of iodide')."

So we might conclude that there's a snare in your organification pathway, and for that the Iodine Docs formulated ATP CoFactors. Each time-release tablet includes Vit B2 100 mg and Vit B3 500 mg.

The suggested daily dose of ATP CoFactors is 1-3 tablets per day, not all taken at the same time. Each tablet can be snapped in two, and I take one half four times a day. It feels better than taking just one whole tablet.

Will this lower your thyroglobulin? I have no idea. This just seems a reasonable place to start.

FURTHER NOTES --
I don't know what to advise since your country does not sell even Vitamins B2 and B3, let alone ATP CoFactors. If you can't buy them and can't import them, find foods that are generally high in Vitamin B. I'm dissatisfied with that answer, but there we are.

Yes, Iodine will make it worse, plus the pink Himalayan salt is loaded with Iodine just 1 gram has 500mcg & we only need trace amounts of 100-150MCG a day. So these people promoting increased Iodine intake is doing so to the detriment of many who don't know the consequences. Always try to find the root cause of a situation first before supplementing. A particular mineral may be good for certain things but will do you no good if your not deficient in it but deficient in another. I always recommend micronutrient testing.I go by that when supplementing. Doesn't test everything but tests a whole lot. You can always do a 24 hour urine iodine $49 buck through labcorp at requestatest.com. if it's high, you'll need to stay away from any extra iodine & keep it to a minimum.Hope this helps.

J Autoimmun. 2016 Dec;75:50-57. doi: 10.1016/j.jaut.2016.07.008. Epub 2016 Jul 21.
Excess iodine promotes apoptosis of thyroid follicular epithelial cells by inducing autophagy suppression and is associated with Hashimoto thyroiditis disease.
Xu C1, Wu F1, Mao C2, Wang X1, Zheng T1, Bu L1, Mou X1, Zhou Y3, Yuan G1, Wang S4, Xiao Y5.
Author information
Abstract
The incidence of the autoimmune thyroid disease Hashimoto thyroiditis (HT) has increased in recent years, and increasing evidence supports the contribution of excess iodine intake to thyroid disease. In this study, we examined the status of autophagy and apoptosis in thyroid tissues obtained from patients with HT, and we determined the effects of excessive iodine on the autophagy and apoptosis of thyroid follicular cells (TFCs) in an attempt to elucidate the effects of excess iodine on HT development. Our results showed decreases in the autophagy-related protein LC3B-II, and increases in caspase-3 were observed in thyroid tissues from HT patients. Interestingly, the suppression of autophagy activity in TFCs was induced by excess iodine in vitro, and this process is mediated through transforming growth factor-β1 downregulation and activation of the Akt/mTOR signaling pathway. In addition, excess iodine induced autophagy suppression and enhanced reactive oxygen species (ROS) production and apoptosis of TFCs, which could be rescued by the activation of autophagy. Taken together, our results demonstrated that excess iodine contributed to autophagy suppression and apoptosis of TFCs, which could be important factors predisposing to increased risk of HT developme