The FastDay Forum

I've just had the results of my latest thyroid function test, the first since starting 5:2 (4:3 for me, actually) and am shocked by the very significant drop in circulating levels of T4 and T3. I have been feeling tired for the past 2/3 weeks, and really cold, but wasn't unduly worried - winter dragging on for ever, etc., but am quite alarmed now and not sure what it means - I don't have a thyroid gland and rely totally on replacement medication; I haven't changed the medication in any way so can only assume that intermittent fasting over the past 3 months or so is responsible for the results.

I was going to do a 3 day fast this week but will have to shelve that idea. My GP has suggested I increase the medication and have a follow-up test in 6 weeks but doesn't have any idea, really, whether or not IF affects circulating thyroid hormones, although he thinks I should stop fasting immediately and just stick to conventional dieting to lose weight (800 calories is his recommendation for me).

Anyone have any thoughts on where I go from here?

Thanks
Marlene

I don't have a thyroid gland either - surgery took care of that a few years ago.

As it happens, I am going to see my GP this afternoon and I am due for a control for my thyroid replacement medication. I'll compare my blood tests results when I get them later this week and I'll update here to let you know how I get on.

I am feeling fine, more energetic if anything, and I don't notice the cold more than I have done in the past.

Could your symptoms be caused by anything else? Anaemia possibly?

Hi Marlene, sorry to hear that!

Just checked my TSH and T4 last week, after 12 weeks of 5:2 and appr. 10% weight loss. I was having symptoms of overdosage, and it turns out I can reduce thyroxine meds. I have attributed this mainly to the change in body weight (it has also happened after conventional diets).

Strange that it should be so different in your case. Theoretically, in my case the improvement could be due to a suppression of auto-immune antibodies. As I may have some thyroid function left (in contrast to you) this could mean that T4 output from recovering cells is increased. However, as far as I have understood the antibodies destroy the thyroid cells, and since I have had this condition for 25 years and needed increasing dosages over time I find that somewhat unlikely. Will check again after a period of non-fasting (summer holidays) to sort out the 2 different effects.

If fasting is the problem, stopping fasting (without the adjustment in meds) should do the trick in a couple of weeks. If fasting is the culprit, and you stop fasting while adjusting meds that might put you in hyperthyroidism. Especially if you continue to lose weight. Personally, I think that one change at a time gives more reliable information. However, 3-day fasts may not be a good thing to throw in the mix right now.

It will be interesting to hear from others. There is still a lot we don't know about side effects of fasting, and background variables may affect side effects.

Strangely enough, my fasting glucose and glycolysed Hb (= long-term average blood sugar) are higher than they have ever been (3 days after last fast). This is strange, given my way of eating and weight loss. Maybe the stress signal of fasting increases glucose - which may not necessarily be good. I know it worked differently for Mosly, but unlike him I was never at risk for type 2 diabetes, so weight loss wouldn't be expected to lower my risk even further.

[Betsysgr8]

My thyroid is essentionally non-functioning. I had radioactive uptake done nearly 20 years ago to treat Graves disease. I do know that when I lose weight my dosage has to be decreased or I have hyperthyroid side effects. I will be getting my bloods done in a couple of weeks prior to my appointment with my endocrinoligist on May 14th. I had been running slightly low and we discussed possibly upping the dosage after this visit.

Did you do a full blood check? Iron, HT, CRP etc? Perhaps something else is responsible and not fasting.

IMO, an 800 calories diet will put you straight into starvation mode. Did you question him about that?

On the other hand, you could sort of compromise 4:3 and your doctor's orders. 800X7=5600
500X3=1500
5600-1500=4100
4100/4=1025
I'd go for 1200 on non-fast days which would keep me on a daily average of 900...

[Betsysgr8]

Marlene, Has your medication changed in any way at all? Is it a generic? Is it absolutly the same? not just dosage but manufacturer? I ask because my endocrinologist had me try some other brands that were much less expensive than the name brand Levoxyl I usually take and on the generics it was as though I hadn't taken any thyroid at all. She explained that I probably don't break down the binders in the generics as well as I do for the name brand.

I used to take my synthroid at different times of day and was getting inconsistent lab results. I started taking it first thing in the morning (as prescribed-duh)on an empty stomach and now my results are very consistent. I get tested 4 times a year and havent needed an adjustment in dosage for some time now. I'm due for check next month so it will be interesting to see how I do with about 6 weeks of 5:2 at that time.

Hmm, interesting and strange predicament Marlene. Add me to the ranks of thyroid-less people. I see my endocrinologist next week, the first time since starting 5:2 and am curious to find out how it's affected me. I'm already on a quite high dose of 200mcg, I'd hate to think I'd have to go higher. As others said, is there any other physical reason for the drop in levels, any new medication you're taking that might affect it? I think mine is so high due to my other meds affecting it and also needing to keep my level in the hyper range for cancer suppression.

[carorees]

I did read a paper showing that fasting affects tissue conversion of thyroid hormones, so the explanation could lie there.

These papers may be relevant: http://www.ncbi.nlm.nih.gov/pubmed/7227325
http://www.ncbi.nlm.nih.gov/pubmed/6381583
http://www.ncbi.nlm.nih.gov/pubmed/577337
The last paper is particularly interesting as it discusses the role of carbohydrates and glucose metabolism in t3 and rt3 production.

I don't take Thyroxine - I take T3 and have been for the past 7 months. I took thyroxine for 30 years following total thyroidectomy but was having unpleasant side effects in the past couple of years and the hypo symptoms had returned. I was taking 200mcg thyroxine. I now take 45mcg T3 - all of the horrible thyroxine side effects have gone but I have reverted from feeling quite well at the beginning of the year to hypo three months later.

It may be that I simply need to increase the T3 slightly but it's a fine balance and I don't want to tip myself into hyper. It's strange because the dose I am on now gave near perfect thyroid function blood results at the beginning of this year before I embarked on 5:2 and now this has changed quite dramatically. As I have no thyroid gland or tissue whatsoever, I'm at a loss to understand what has caused this turn around.

I am a member of an on line thyroid support group and have posted on there, asking for advice - they are very knowledgeable and I believe several of them have been doing intermittent fasting in one form or another. Will wait and see what feedback I get from there and pass on anything of use.

Thanks everyone for your comments and concern - very much appreciated.

I did read a paper showing that fasting affects tissue conversion of thyroid hormones, so the explanation could lie there.

These papers may be relevant: http://www.ncbi.nlm.nih.gov/pubmed/7227325
http://www.ncbi.nlm.nih.gov/pubmed/6381583
http://www.ncbi.nlm.nih.gov/pubmed/577337
The last paper is particularly interesting as it discusses the role of carbohydrates and glucose metabolism in t3 and rt3 production.

You really are a wizard, Caroline! Where do you find this stuff? Very, very interesting and informative, not least to discover in the first study that the participants were being given a dose of between 60-80 micrograms of T3, which seems huge to me. Also, it highlights the thorny and complicated issue of rT3 and I have a nagging suspicion that;s where my problem lies. But what to do about it?

Thanks very much for that useful information.

Interesting, Caroline! I was having palpitations and feeling jittery, TSH was very low, and T4 increased, so I would think reducing meds was correct in my case anyhow. Will check T3 next time, in a couple of weeks.

Seems no one looked at this since the eighties The fasts in the study were rather more drastic than 5:2, but one of the articles also mentioned calorie-restricted diets in general.
So going on an 800 kcal diet may not be the way to resolve this.

Personally, I would choose to pause the weight loss for a while to get this sorted out, then slowly start with one intervention at a time with relatively close monitoring (requiring a sympathetic health care provider). But I do not know anything about your weight, goals and motivations, Marlene. Keep us posted how it goes and if you learn anything else. Good luck!

[carorees]

Glad I could help! I find the info on pubmed, but it helps that I've 20 years of literature searching experience

Good thing that my thyroid seems to be better after I started fasting because I don't understand a single thing of what you girls are talking about!
Nothing positive though until my next blood tests in about a month.

So going on an 800 kcal diet may not be the way to resolve this.

Just what those of us with thyroid issues don't want to hear when we're already having trouble losing weight! Hopefully you can get whatever is up sorted out Marlene.