Friday 16 November 2018

Always chilly? From an underactive thyroid to Raynaud's disease here are some possible explanations

Why do some people to feel the cold more than others? From an underactive thyroid to Raynaud's disease, Jamie Ball investigates the possible explanations

Poor circulation, which generally affects middle-aged and older people, contributes to a poor tolerance of the cold.
Poor circulation, which generally affects middle-aged and older people, contributes to a poor tolerance of the cold.

'A jumper is something a parent puts on a child when the parent feels cold." Ever heard that one? For anyone from early-middle age onwards, the wisdom of that witticism grows warmer each year.

What is less well known, however, is why some of us from the outset feel the cold worse than others, and why the elderly must suffer the worst.

Poor circulation, which generally affects middle-aged and older people, contributes to a poor tolerance of the cold. If the flow of blood has difficulty getting to the heart or down to your leg muscles, it will be keenly felt first in your extremities; mainly your fingers followed by your toes, then even your ears and nose.

At the most simplistic level, any hot spice can stimulate your circulation.

A sensitivity to cold is a symptom of an underactive thyroid
A sensitivity to cold is a symptom of an underactive thyroid

According to the health-food store, Holland & Barrett, "try chilli or a pinch of cayenne pepper in tomato juice, or added to a hearty soup. Horseradish or black pepper are also said to have circulation-boosting properties, while ginger can help warm you up and get your blood moving in the right direction."

Why that might work for some, the issue of thermoregulation for most of us is decidedly more complex. The cold brings out the worst in us.

If our skin temperature is greater than that of our surroundings, the body loses heat by radiation and conduction, and this is what may happen next.

Arterioles carrying blood under the surface of the skin constrict, rerouting blood towards the warmer core of the body to prevent the blood from losing heat, while preventing our core temperature dropping further. Tiny muscles (called arrector pili) under the surface of the skin contract, lifting the hair follicle upright. This acts as an insulating layer, trapping heat and creating what we commonly call "goose bumps."

Furthermore, muscles receive messages from the hypothalamus in the brain to start shivering, which increases heat production more effectively than exercise.

The Known Unknowns of Thermoregulation

Some feel the cold more than others
Some feel the cold more than others

Dr Ronan Murphy is deputy head at the School of Health and Human Performance in DCU, Principle Investigator of the Integrative Cell and Molecular Physiology Group and vie-chair of Epigenetic Technologies.

"Why there are thermoregulation defects as we age is a question that has been asked for a long time," says Murphy. "More than ever, it's a very important question, because as our population ages, our understanding of how bodies thermoregulate and respond to environmental temperature changes becomes paramount."

He says there are three big questions scientists are asking about why such thermoregulation defects happen as we age.

Firstly, is it because as we age, our capacity to sense temperature is compromised? As in, are our sense mechanisms that signal back to the brain being compromised? For example, do you not know that the temperature of the room you're in is, for example, cold or warm, thereby potentially exposing you to hypothermia or hyperthermia?

The second question relates to how our thermoregulation capacities are limited as we age.

Our ability to keep warm is down to a number of systems, all of which degenerate as we age.

The most obvious of these is the cardiovascular system that carries blood around the body.

The third question is, as we age, are we less physically tolerant of extremes of temperature than a younger person naturally is?

Murphy stresses that getting to the bottom of these questions is complex and manifold: much like brain research, there are so many compounding factors feeding into thermoregulation that it's very challenging to tease out the separate strands of what, exactly, is causing what symptom.

It is, he says, more like trying to unlock a three-dimensional puzzle than a one-dimensional pathway.

"What we do know is that there's a link between your neuro-cognitive capacity and its signalling with your thermal regulation, via regulation of our endocrine system.

To have a fully-functional thermoregulatory process, you need to be metabolically fit.

To try counteracting the processes of aging, you need to be physically active and physically fit, with a good diet.

There's obviously nothing you can about your chronological age, but you can biologically age better, and a healthy lifestyle is central to prolonging your thermoregulatory capacity."

Murphy says that one of the areas under investigation is heat loss, part of which is researching whether, as our skin degrades with time, its insulation properties deteriorate, leading to increased heat loss.

"We're ageing longer; we're living well into our 80s and 90s now, and our generation may live a decade longer.

It's well known that for people towards the end of life, if you feel their hands, or their extremities, they feel really cold," says Murphy.

"As the body ages, everything slowly withdraws into the core, to keep the body alive.

Their ability to self-regulate and respond appropriately may actually decrease, so they may actually be cold, but that's not to say they can't feel the heat, because their sensory mechanism isn't there either."

Murphy says another behavioural factor that effects thermoregulation is sleep.

We all have circadian rhythms with a clear diurnal modulation. As we've all experienced, sleep plays an essential role in resetting and calibrating our body clock every 24 hours.

However, if you're experiencing broken sleep patterns each night, as so many elderly people do, it has a hugely negative impact on our overall physiological health and, in turn, our thermoregulatory processes.

It may be worth finding out, at a visit to the GP, whether you, like up to 4pc of others, have Raynaud's disease; a medical condition in which a spasm of arteries triggers periods, ranging from minutes to hours, of reduced blood flow.

Raynaud's typically involves fingers or toes. Such extremities (along with ears and nose, in acute cases) will turn white or even blue, frequently leading to numbness or pain. Then, as the blood returns to the area, the fingers or toes turn reddish, often accompanied by swelling, tingling or a painful pins-and-needles sensation. But it's worth trying to distinguish Raynaud's disease (ie. primary Raynaud's) from Raynaud's phenomenon (ie. secondary Raynaud's).

Raynaud's disease, which is often coined as "being allergic to the cold", typically develops in the teens or early adulthood (more often in women than men) and is understood to be at least partly hereditary. However, Raynaud's phenomenon occurs secondary to a wide variety of other conditions, and usually affects older people.

In both cases, the most recommended treatment is simply avoiding the cold.

Of the 10 most common symptoms of an underactive thyroid (the throat gland which helps hormones control our growth and metabolism), sensitivity to cold is listed first on the HSE's website.

If you find you're also susceptible to some of all of the other nine symptoms (ie. weight gain, constipation, depression, tiredness, slowness in body and mind, muscle aches and weakness, muscle cramps, dry or scaly skin and, finally, brittle hair and nails), then it may be worth visiting your GP to ask for a blood test.

This is because a thyroid function test, which looks at the levels of thyroid-stimulating hormones and thyroxine in the blood, is the only accurate way to find out if there is a problem with your thyroid.

Raynaud's disease: Syndrome or phenomenon?

It may be worth finding out, at a visit to the GP, whether you, like up to 4pc of others, have Raynaud’s disease; a medical condition in which a spasm of arteries triggers periods, ranging from minutes to hours, of reduced blood flow.

Raynaud’s typically involves fingers or toes. Such extremities (along with ears and nose, in acute cases) will turn white or even blue, frequently leading to numbness or pain. Then, as the blood returns to the area, the fingers or toes turn reddish, often accompanied by swelling, tingling or a painful pins-and-needles sensation. But it’s worth trying to distinguish Raynaud’s disease (ie. primary Raynaud’s) from Raynaud’s phenomenon (ie. secondary Raynaud’s).

Raynaud’s disease, which is often coined as “being allergic to the cold”, typically develops in the teens or early adulthood (more often in women than men) and is understood to be at least partly hereditary. However, Raynaud’s phenomenon occurs secondary to a wide variety of other conditions, and usually affects older people.

In both cases, the most recommended treatment is simply avoiding the cold.

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