Some time in the next month, I am going to become a cretin. My future has already been vividly described by the detective writer Dorothy L. Sayers in The Incredible Elopement of Lord Peter Wimsey. A beautiful, intelligent woman marries her loathsome doctor, and one day her broken-hearted former lover finds her living like an animal in the remote Basque mountains, “the face white and puffy, the eyes vacant, the mouth drooled open…a dry fringe of rusty hair [clinging] to the half-bald scalp.” From his description, Lord Peter Wimsey recognises the symptoms of thyroid deficiency, or hypothyroidism. He travels to Spain, secretly feeds the woman thyroxine, and she is restored to her former self.

That story has always haunted me, partly because when my daughter Leonora was diagnosed as congenitally hypothyroid as a new-born baby. This butterfly-shaped gland in the neck regulates your metabolism and affects every organ in the body, including brain, heart, skin, intestines and muscles. Without a tiny white pill of thyroxine every day, she would grown up as a dwarf and a cretin, not a tall, beautiful, brainy pupil at North London Collegiate.

Strangely, Leonora wasn’t the only one to have something wrong with her thyroid. An oncology nurse at the hospital scrutinised my throat and asked if I’d ever had my own levels checked. No, I said. That was almost twelve years ago, and it has taken until this year for my own thyroid cancer to be spotted.

I was pretty sick after both my babies were born, and my son was ill, too, with kidney problems. I went on working. I survived an attempt to stop the publication of my third novel, A Vicious Circle, by a boyfriend I hadn’t seen for fifteen years who terrified Penguin into cancelling it. My son got better, and I published a fourth novel. But the nurse’s concern stuck in my mind, because I was exhausted all the time, and putting on weight. I asked my GP, twice, if there could possibly be anything wrong with my thyroid, and he sent off a blood test. It came back as normal. Three years ago, I paid to have my thyroid scanned in the basement of a Harley St. clinic. Yes, I was told, there were four or five small lumps. Nothing more was said about these, other than the specialist congratulating my GP for spotting them in my throat. Oh well, I thought, I just have a lumpy thyroid.

Nobody suggested a biopsy to see if the lumps were malignant. Nobody suggested another scan to see if the lumps were growing. Thyroid cancer is quite rare – only 1,300 cases in the UK. I crawled away feeling guilty for causing a fuss. I had evening primrose oil suggested for my devastatingly heavy periods, and cognitive therapy for my depression. I took the former, but not the latter. Depression comes with the territory if you are a novelist.

Last year my fifth novel, Love in Idleness, came out. It was a romantic comedy based on a Midsummer Night’s Dream, and a joy to write. Other people seemed to like it a lot, too, I had a wonderful new publisher, my children were finally sleeping through the night and I felt completely happy. Yet I was still really, really tired – and still putting on weight. My periods were so heavy that I had to put a plastic bag under me when I drove, because every other protection would be soaked through in 20 minutes. My husband kept nagging me to see a doctor but I’d burst into tears and say I’d been told I was perfectly healthy.

One day, however, Eleanor Mills, my friend and editor on another newspaper, rang. I was, once again, too ill to write for her.
“ Amanda, something is wrong with you,” she said in her most inexorable voice. “Go and see my doctor in Harley St.”
Very reluctantly, I did so. I have BUPA (it comes with my husband’s job) and feel a guilt about it that most readers will probably understand. Oddly, Dr. Anne Coxon did too. In our 40 minute consultation, during which she took several blood samples and made quite sure I wasn’t bonkers, she was gentle, sensible, wise and talked to me as a person not another tiresome slot in a 7-minute schedule.

A week later I heard Dr. Coxon’s voice telling me that antibodies had come up in my blood-test connected to my thyroid. Off I went again to another basement in Harley St, to have gel smeared over my throat and a Professor Bartram looking at it on ultrasound. The next day (it was all so quick if you paid, I couldn’t get used to it) I was told I had some lumps in my thyroid.
“ Oh yes,” I said, unpeturbed; “I know about those.”
But this time, Dr. Coxon did what my NHS doctor failed to do. She asked for a biopsy.
“ It’s only a 5% chance of cancer,” she said, “but I’d just like to be sure.”
Having a biopsy taken of something in your throat is not nice. You get a local anaesthetic injection, and then a needle gets pushed in deep and fluid taken out. The needle, guided by the scan, hurt, but although I had a sore throat for a week after I thought this was all just a precaution. Two days later, I discovered it was not.

“The good news is that it’s the commonest kind of thyroid cancer, the papillary,” said Dr. Coxon’s cheerful voice. “But you’ll have to have your thyroid out. You’re going to have about five days in hospital, and I’m afraid it won’t be very comfortable.”

I had an MRI scan, one of the most horrible hours that I’ve experienced – lying in a white plastic coffin with headphones playing Classic FM, while a noise like a pneumatic drill vibrated at different frequencies for several minutes at a time through my body. The scan extended to my heart and lungs, and showed a big shadow over one of my breasts. A not-so-cheerful Dr. Coxon arranged for me to have a mammogram immediately. I must have looked awful going in, because two complete strangers stopped me in the street to ask if I was alright. The one good thing about being seriously ill is discovering just how kind people can be.

I did not have breast cancer, only thyroid cancer. The joy of this was such that I felt slightly ashamed of making any fuss. I learnt now that if you have to have cancer, mine is a great one to have. The thyroid absorbs iodine. Some smart doctor realised that if you give a patient radioactive iodine, it seeks out and destroys any remaining thyroid cells. The nightmare with all cancers is that even if you take out one tumour, it can seed itself elsewhere in the body to grow again. With the thyroid, however, you don’t need clumsy, poisonous chemotherapy. You have what all oncologists dream of giving their patients – a magic bullet, or potion, which kills the cancer but leaves everything else unaffected.

Providing, that is, you have the thyroid out first. Mr. Lynn was spoken of by other doctors with such reverence as the best thyroid surgeon in Britain, that being his patient felt like an honour. He was gentle, kindly, and like his team, utterly professional. I immediately trusted him, which was just as well, because he was going to cut my throat.

It was excruciating. Worse than childbirth, worse than my emergency appendectomy two months previously, worse than migraine. I felt if I nodded, my head would fall off. Even with a morphine drip – which, after the first night I got removed because it was sending me insane – the pain was such I could hardly drink. Mr. Lynn had removed two malignant carcinomas, one “huge” and difficult, stuck to my voice-box, which was now badly bruised. I could only whisper for several weeks and still have a weak, croaky voice. I couldn’t breathe properly, and had to have an oxygen mask. I looked like Frankenstein’s monster, with huge stitches across my neck. A completely wonderful nurse, Shirlette, looked after me as if I were a baby. I got out of the Charing Cross Hospital three days later, with the thyroxine tablets I’ll have to take forever, and radiotherapy still to come.

Between them, Dr. Coxon and Mr. Lynn saved my life. The cancer hadn’t spread to my lymph glands or worse, my spine; it was papillary, the commonest kind of thyroid cancer which, if caught in time when you are under 45, gives you a completely normal life-span. Unlike medullary thyroid cancer, which is caused by a faulty gene or anaplastic cancer, connected to old age, papillary thyroid cancer is caused by radiation. Where can I have been exposed to that? Well, in France and Italy, where cases of thyroid cancer have radically increased in the past decade, doctors are convinced it is caused by the fall-out from the explosion at Chernobyl nuclear power station, 20 years ago. The specialist I saw at the Royal Marsden hospital where I am going to have radiation therapy pooh-poohed this, but other doctors I’ve spoken to aren’t so sure.

All of this makes me extremely worried for other, undiagnosed, sufferers out there, particularly other women as this cancer affects about ten times more women than men. I was completely failed by my GP, but saved by my husband, friends and two doctors I could pay to see. What if you have none of these?

Two months later, I am still exhausted, but I have gone down a dress-size. My periods are no longer crippling. I feel better in myself than I have done for years. My scar is now a thin red line. There is more misery to come, when I will have to stop taking the thyroxine pills for a week in order to stimulate absorption of radioactive iodine. I will have to spend four days in isolation as the radioactivity passes through my body, emerging in sweat, saliva and urine. I will be a cretin – but only for a fortnight, until I take thyroxine again. Then I, like the woman in Dorothy L Sayers’s story, will be back – smaller, sharper and very angry.