Low Vitamin D - Thyroid Question

[packers52]

I just had labs run again this week, I have hypo symptoms.  I saw the NP instead of my regular Dr. and she suggested that we run vitamin D.

TSH: 3.79 (.34 - 5.6)
FT4: .90 (.58 - 1.64)
Vit D: 18 (30 - 80)

With the vitamin D low she has prescribed a Vit D supplement, take this for 8 weeks then re-run labs.  They also say that these Thyroid tests are normal :-)

My question is can the Low Vitamin D cause the slightly Hypo Thyroid numbers, or does the slightly Hypo Thyroid cause the low Vit D?

[gimel]

Just to supplement the good info already given to you, I wanted to mention that in the future you should also request to be tested for Free T3 and Vitamin B12 and ferritin.  Free T3 is very important because it largely regulates metabolism and many other body functions.  Scientific studies have also shown that it correlated best with hypo symptoms, while Free T4 and TSH did not correlate.  

A good thyroid doctor will treat a hypo patient clinically by testing and adjusting Free T3 and Free T4 as necessary to relieve symptoms, without being constrained by resultant TSH levels.  You can get some good insight into clinical treatment from this letter written by a good thyroid doctor for patients that he sometimes consults with after initial tests and evaluation.  The letter is then sent to the participating doctor of the patient to help guide treatment.  In the letter, please note the statement, "the ultimate
criterion for dose adjustment must always be the clinical response of the patient."

http://hormonerestoration.com/files/ThyroidPMD.pdf

[packers52]

Thanks for the comments; and information!

:-)

[Red_Star]

The listed possible explanations for why vitamin D deficiency is common with hypothyroidism: poor absorption of vitamin D from the intestine or the body may not activate vitamin D properly.

A study published in the journal Thyroid reported that Vitamin D deficiency is much more common with Hashimoto's thyroiditis (92%) compared to the general population (63%). The study: "Relative vitamin D insufficiency in Hashimoto's thyroiditis."

[goolarra]

Vitamin D is essential for the metabolism of thyroid hormones.  Which came first, or is there even a causal relationship???  

You want your D well up in the range, not just barely.

Your FT4 is still a little low...only 30% of range.  Using a more reasonable TSH range of 0.3-3.0, your TSH is also a little high.  There's plenty of room for an increase in your labs if you still have hypo symptoms.  Be aware, though, that hypo and vitamin D deficiency can have many of the same symptoms.