RxISK Stories: ‘Till Birnam Wood Come to Dunsinane or Women Gain Weight on Thyroxine

If there is one thing most doctors think they know its that weight gain can be caused by an underactive thyroid and having an overactive thyroid leads to weight loss. So the thyroid hormone, thyroxine, will lead to weight loss. And magazines, newspapers and websites, especially in the United States openly invite anyone who is overweight to get their thyroid checked. Thyroxine is now one of the three most commonly prescribed drug groups in the UK.

Q’s story

I am a doctor and was working as specialty trainee for the last three years when it all started going pear shaped (literally). I consulted my GP with complaints of extreme tiredness, weight gain, hair falling out and dry skin.  She suggested a blood check including glucose levels and importantly thyroid function. The results came back showing I have an underactive thyroid. I was started on thyroxine with an initial dose of 50 mg which gradually went up to 125 mg. To my surprise I started to gain weight. I have always had weight problems but not as uncontrolled as this.

There have been a few times I have stopped taking thyroxine, usually if I am ill with something else and I forget. When I go back on it I gain the weight again. Recently when I was not very regular taking my thyroxine I noticed a marked reduction in my weight of around 3-4 KG over a period of 3 weeks .

I always thought that thyroxin tablets will do the same job as the natural hormone your body produces. Restoring my thyroid hormone levels to normal I thought was going to get my weight levels back to normal.

Everything in every medical textbook says that having an untreated or under-treated underactive thyroid can lead to weight gain and once thyroid levels are stable and back within the normal range, the expectation is that one should be able to lose the extra weight again. But unfortunately that is not the case. Some of my other symtoms including hair loss, and dry skin have not improved either. But there has been some improvement in tiredness and body aches.

I keep a regular account of my food intake, and calorie count. I eat sensibly. I sometimes skip meals and have reduced my daily calorie down to 1500 a day on average for the last 3 years but with minimal response.

I think of discussing it with my GP, but I am sure she is going to respond with a grin, and I doubt if she will believe me – no doctors do. The other thing is that I don’t really have any choice. The options are lying in bed all day, exhausted, with body aches  and feeling miserable or taking the tablets. I can’t afford to be lazy or complain, or moan all day, because I have two young children to look after and work fulltime as hospital doctor, which itself is quite stressful.

RxISK Response

I didn’t believe this when I heard about it first. I’ve asked several doctors since and none believe that thyroxine could cause weight gain. But almost immediately after I heard about it, perhaps coincidentally I became aware of several patients of mine, all women, who had gained substantial amounts of weight and all on asking had been put on thyroxine. In a number of cases on the basis of blood tests, when there were no clinical signs that they were actually hypothyroid.

Going into RxISK, there were over 600 reports of weight gain with a PRR value of over 4, a clear signal that thyroxine was producing this problem. A quick search shows there are a number of forums where this issue has come up – thyroid help.org, healthy pages, med help.org,  and gransnet.