For many years, Sarah O'Neil, 34, a mother of three, was so unwell that she presumed she was dying. Given that her condition left her bedridden and in a wheelchair, and doctors were baffled as to what was wrong, it is easy to understand why she feared the worst.
"Every week, my children used to say to me, 'Mummy, are you going to die?' I always told them, 'No', but, inside, I was just as scared as they were.
"At my worst, my life just totally went to pot. I could feel my heart thumping in my chest all the time and it had reached a point where even breathing was an effort. I was sleeping at least 20 hours a day."
But, in the past three months, Sarah's life has been transformed. In April, she decided to make a visit to Dr Barry Durrant-Peatfield, a private, Surrey-based former GP whose book on thyroid problems she had taken out of the library in 2003.
Dr Durrant-Peatfield, who works outside the NHS, is a controversial figure in thyroid medicine, offering treatments that are actively opposed by many endocrinologists. He has a reputation for making radical claims, such as his belief that up to half of patients presenting to their doctors with depression are actually depressed because of undetected imbalances in their thyroid. As a result of his thyroid supplementation treatment, Dr Durrant-Peatfield claims an ability to improve the majority of his patients' health within weeks.
"Sarah's situation was extreme," says Dr Durrant-Peatfield. "Most people I see have milder symptoms such as constant coldness, fatigue, lethargy and a feeling of being unwell.
"People with thyroid problems generally get steadily worse over time. Sadly for Sarah, a typically casual response from her GP had seen her head a long way down that scale before she finally came to me for help. She never needed to end up so unwell. She could have been helped much sooner."
Sarah, who lives with her husband Martin, 34, an IT consultant, and children Rebecca, 13, Samuel, 10, and Daniel, eight, in Watford, was suffering from hypothyroidism, or an underactive thyroid. Now, not only does Sarah finally have a diagnosis, but also an apparent cure, thanks to a relatively simple regime of supplements and medication.
Located in our neck, the thyroid gland is one of a family that makes up our endocrine system. It contains the only cells in our body capable of absorbing and synthesising iodine, and also secretes hormones, such as thyroxine, that act as chemical messengers, telling organs and tissues what to do.
It plays a vital role controlling our metabolism and the conversion of oxygen and calories into energy. Symptoms of hypothyroidism including excessive tiredness, weight gain, constipation, aches and pains, feeling cold, dry skin, memory loss, reduced libido and depression. Hypothyroidism affects an estimated 1 in 50 women and 1 in 1,000 men in the UK.
"The sad truth for sufferers is that, with symptoms so general, they are usually sent away from their GP and told they're suffering from stress or depression," says Dr Durrant-Peatfield. "They're put on Prozac that does nothing to help the true cause."
Sarah first started feeling unwell in 1999, when she noticed that she was becoming more tired than usual. "Up to then, I'd been in good health, although I was very busy and often tired after running around after three small children, looking after the house and running my own office-cleaning business," she says. "But suddenly I felt exhausted in a way I'd never known before. I kept getting repeated sore throats and colds and also felt physically and mentally exhausted.
"By the start of 2000, I was so tired I was quite literally ready for bed at half-six in the evening. I felt as though I was slowly sliding off the face of the planet. I went to my GP, who referred me to an endocrinologist. But there, I was given short shrift. I was told that of course I'd be tired with three children to look after.
"Then they suggested that perhaps it was a return of the post-natal depression I'd had in 1994 following the birth of my eldest, and asked if I wanted to be referred to a psychiatric doctor. I replied, 'I'm tired, not depressed or mad.'"
Sarah now knows that the depression is a common symptom of hypothyroidism and is likely to have been her first obvious sign of her thyroid's malfunction.
Over the coming months, she struggled to cope. "I felt as though I was just about managing to keep my head above water. I had no idea who to turn to or where to go to get help, but I knew I wasn't imagining what was happening. I was getting weaker and weaker. I had to sell my business as I simply couldn't function."
In 2001, Sarah returned to her doctor and asked to have blood tests. Having done research on the internet and at the library, she'd begun to suspect her thyroid could be the problem. Her blood tests showed the thyroid function was bordering on low.
"But again, the doctor just told me to go home, rest and that everything would sort itself out," she says. "I became a total nightmare to live with. I was constantly weepy and short-tempered with both frustration and worry - both are also typical symptoms of a thyroid problem.
"My husband also had to take over many of the household chores and cooking, as I was simply no longer able to do them. It was all I could do to get the children to school, and then I would sleep all day until it was time to collect them again."
In September 2003, Sarah reached breaking point. "My marriage was by that point under huge strain. I honestly wouldn't have blamed my husband if he'd walked out on me there and then. I'd lost most of my friends, too. I mean, to be honest, there aren't many people who find it fun to sit on a bed in a dark room with someone who can barely speak.
"My GP did further blood tests and sent the results to the endocrinologist for a second opinion, but he replied, 'I don't need to see this lady.'"
That October, Sarah and her husband decided to pay privately to see a different endocrinologist. Again, her concerns about her thyroid were dismissed. This time, she was diagnosed with ME. "Afterwards, when my husband and I got into the car, I burst into tears and cried all the way home. ME felt like a life sentence with no cure and little treatment.
"For much of 2004, I lay in a darkened room and slept for 20 hours at day," says Sarah. "I couldn't even get up to go to the loo - I literally had to crawl there on my hands and knees. We got a wheelchair from the Red Cross so I could occasionally leave the house, which was the last thing I'd ever expected I'd have to do in my early thirties.
"Even going to the park in the wheelchair for three hours a day became like a military operation. I had to sleep even longer in the days preceding such a trip to build up the energy for it. I couldn't even hold a fork either - my husband had to feed me."
Following two long years during which her life was on hold, a visit to Dr Durrant-Peatfield was, for Sarah, a last resort.
He believes that standard thyroid function tests used by the majority of doctors are unreliable. He recommends heavier reliance on the "basal temperature test", which involves measuring the internal temperature on waking - a test he describes as "derided" by many conventional doctors, who maintain that blood tests for thyroid function are reliable, and that it is the basal temperature test that is misleading.
"The basal test has been used since 1945. It says that if anyone's temperature falls below 37 degrees on a permanent basis then they invariably have a reduced metabolic rate which needs investigation," says Dr Durrant-Peatfield. "In my experience, this reduced rate is usually as a consequence of an underactive thyroid. I also use a subsequent test called the adrenal stress index, which is where I really fell out with establishment doctors. The adrenal gland is vital to help the body cope with stress and is often impaired in the patients I see. Its function needs to be restored in order to help the thyroid gland.
"It's not that I totally disregard blood tests. I just don't take them as the be-all and end-all. What is more important to me are the symptoms described by the patient and the results of the two tests I consider more relevant."
Sarah says: "I went along [to see Dr Durrant-Peatfield] with all the results of my blood tests from the previous years. We sat and chatted for about 20 minutes, he looked at my blood tests then said to me, 'This is really easy to tweak.' He said I had a clear case of Hashimoto's disease, an auto-immune inflammation of the thyroid gland in which it is slowly destroyed by thyroid antibodies. He added Hashimoto's had led to hypothyroidism, which he believed was responsible for all my symptoms.
"My husband was very sceptical. Afterwards, he said the doctor was cruel to raise my hopes in such a way. But I felt inside that my life was about to change for the better."
Patients who are diagnosed with hypothyroidism are normally given supplements of synthetically produced hormones to make up for the deficiency. But Dr Durrant-Peatfield prefers using a natural form of thyroxine derived from cows or pigs. In just three weeks, Sarah noticed a difference.
"I felt as though a veil was slowly being lifted from me," she says. "I hadn't even realised how severely the condition had affected my vision. But suddenly everything seemed brighter and more in focus. By the beginning of June, I was spending far less time asleep and was able to walk again and leave the house. I could go to the supermarket again and take the children shoe shopping.
"Two weeks ago, I chased my three children up the stairs to the top of the house. It sounds really silly, but by the time we reached the top we were all crying as we all realised I am truly getting better. Next week, we're going swimming for the first time in years.
"My husband is still a little doubtful. He can't believe after all I've been through I'll be as well as I once was. But I can feel how my body is changing and I know I'm getting better and better every day. For the first time in years, my life is good."
Your Thyroid and How to Keep it Healthy by Dr Barry Durrant-Peatfield, Hammersmith Press, £14.99Reuse content