Do you have an un­der­ac­tive thy­roid?

La Semana - - TEMAS - BY DR MICHAEL MOSLEY

Hy­pothy­roidism - or an un­der­ac­tive thy­roid - af­fects one in 70 women and one in 1,000 men ac­cord­ing to the NHS. But it can be a tricky dis­ease to di­ag­nose and treat. Dr Michael Mosley, of Trust Me I'm a Doc­tor, asks if suf­fer­ers are slip­ping through the net.

Some­one emailed me the other day to ask me if I had ever con­sid­ered the pos­si­bil­ity that I might have hy­pothy­roidism; an un­der­ac­tive thy­roid. The rea­son he con­tacted me is be­cause he had seen me on tele­vi­sion and no­ticed that I have quite faint eye­brows, which can be a sign of this dis­or­der.

I have none of the other symp­toms such as weight gain, tired­ness and feel­ing the cold eas­ily, so I've de­cided not to go and get my­self tested.

But if you do - and you think you could you have it - what should you do about it?

To get some an­swers I've been talk­ing to Dr An­thony Toft, who is a for­mer pres­i­dent of the British Thy­roid As­so­ci­a­tion.

He tells me that the thy­roid gland is a bit like the ac­cel­er­a­tor pedal on your car. It pro­duces hor­mones which help con­trol the en­ergy bal­ance in your body. If it's un­der­ac­tive, then your meta­bolic rate will be slower than it should be. This means that you are likely to put on weight. Other symp­toms can in­clude feel­ing too cold or too hot, lack­ing in en­ergy, be­ing con­sti­pated, low mood, poor at­ten­tion or "brain fog".

The main hor­mones in­volved are thy­roid stim­u­lat­ing hor­mone (TSH), T4 and T3. TSH is re­leased by the pi­tu­itary gland and tells your thy­roid to get go­ing.

In re­sponse your thy­roid should re­lease the hor­mones T4 and T3. T4 is con­verted in your body into T3, the ac­tive hor­mone that revs up your cells.

If you have symp­toms of hy­pothy­roidism then your GP will prob­a­bly test your blood. The signs they're look­ing for are high lev­els of TSH, to­gether with low lev­els of T4.

If your TSH is higher than nor­mal this sug­gests that the gland that pro­duces this hor­mone - the pi­tu­itary gland - is work­ing hard to tell the thy­roid gland to pro­duce more hor­mone, but for some rea­son the thy­roid gland is not lis­ten­ing.

The pi­tu­itary then ups its game and pro­duces more and more TSH, but T4 lev­els stay low.

So if you have a high TSH cou­pled with a low T4, it's likely that the body is say­ing "I need more thy­roid hor­mone!" but the thy­roid gland isn't do­ing what it's be­ing told. The re­sult is hy­pothy­roidism.

When this hap­pens pa­tients are of­ten pre­scribed levothy­rox­ine (T4). Symp­toms di­min­ish and pa­tients are happy.

So if it's so straight­for­ward, why are there so many fo­rums full of dis­sat­is­fied pa­tients? Why do we at Trust Me get so many emails about this sub­ject?

One of the is­sues with the blood tests is that there are no stan­dard in­ter­na­tional ref­er­ence ranges. In the UK, for ex­am­ple, we set the bar rather higher than many other coun­tries. "If the T4 is right down at the lower limit of nor­mal," he says, "and the TSH is at the up­per limit of nor­mal, then that is sus­pi­cious. It doesn't of­ten arouse sus­pi­cion in GPs, but it should."

He is also con­cerned that when a GP does di­ag­nose an un­der­ac­tive thy­roid, then pa­tients are al­most al­ways pre­scribed a syn­thetic ver­sion of T4.

This works most of the time but in some cases the symp­toms don't im­prove. This might be be­cause with some pa­tients the prob­lem is not an un­der­ac­tive thy­roid, but the fact that they can't con­vert enough T4 into the ac­tive hor­mone T3.

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