For the best part of 2025, I was deeply exhausted, fighting insomnia most nights and withstanding a strange, buzzing anxiety. My concentration tanked; I regularly lost my train of thought mid-sentence, and my brain continuously raced. Family noticed changes in my speech – slowing, even slurring at times – and my voice continually became hoarse.
Usually very energetic and sociable, I struggled to gear myself up for exciting events and trips. I saw less of my friends, and stopped exercising. A low mood settled in and wasn’t lifting with time.
I put a lot of it down to bereavement. I lost someone very close to me in spring 2025, when I was 35, and I assumed the fog and physical heaviness were simply what deep grief felt like. I went to my GP in the UK reporting insomnia – my worst symptom – alongside brain fog and anxiety. I was pointed towards therapy, offered a few nights’ worth of sleeping tablets, and twice urged to try antidepressants. But the problem felt physical to me, and I wanted to tackle it without medication.
It wasn’t until I started the process of freezing my eggs, almost a year after the bereavement, that I got a different answer.
I live between London and Lisbon, and in February this year, at 36, I had a full pre-fertility blood test done in Portugal. It flagged something I hadn’t considered: my thyroid. My thyroid-stimulating hormone (TSH) reading came back at 0.008 – dramatically, almost implausibly low. The fertility doctor I’d been working with was baffled and encouraged me to find an endocrinologist.
Back in the UK a month later, I asked for a thyroid test through the NHS. That result was 0.38 – I was told I was “in range” (the reference range 0.35-4.94), despite being right at the bottom edge of “normal”, and still feeling markedly unwell.
Retesting in Portugal, the picture shifted again. My TSH had swung to 7.071 – now above the range in the opposite direction. Four days later, it had climbed to 9.44. My anti-thyroglobulin antibodies (anti-TG) were tested, too – a marker of thyroid autoimmunity and a sign the immune system may be attacking the thyroid. This was the lightbulb moment: mine were more than 11 times the upper limit of normal.
The NHS test had looked for a different antibody, anti-thyroid peroxidase (anti-TPO), and it came back clear. My Portuguese endocrinologist immediately spotted what this meant: Hashimoto’s thyroiditis.
Hashimoto’s is an autoimmune condition where the immune system attacks the thyroid gland itself. According to the British Thyroid Foundation, one in 20 people in the UK live with a thyroid condition – and Hashimoto’s causes 9 in 10 cases of underactive thyroid.
I was prescribed levothyroxine – medicine for an underactive thyroid. The endocrinologist drew me a diagram explaining the ‘swing’ from low to high, and assured me I was “subclinical” – an early stage where the disease is active but hasn’t yet tipped into full-blown thyroid failure.
Left untreated, an underactive thyroid can affect far more than energy and mood. According to the NHS, it’s linked to a higher risk of heart problems, including coronary heart disease and heart failure, and can weaken bones over time, raising the risk of osteoporosis.
For women trying to conceive or already pregnant, untreated thyroid dysfunction can disrupt ovulation and the menstrual cycle; during pregnancy it’s linked to a higher chance of complications including high blood pressure, birth defects, premature birth and miscarriage.
Hashimoto’s often runs in families, according to the British Thyroid Foundation, and having another autoimmune condition – coeliac disease or Type 1 diabetes, for example – slightly raises the risk of developing it too. The standard treatment is levothyroxine (what I was prescribed) – a synthetic version of the hormone the thyroid isn’t making enough of – usually taken daily, often for life.
On treatment, my symptoms began to improve – I felt lighter, sleep came more quickly, and it was easier to concentrate on work. But my GP in Britain still doubted my Hashimoto’s diagnosis. My endocrinologist reassured me: “You have Hashimoto’s disease. And you had values of TSH >6. That’s the reason why I put you on levothyroxine.”
What could have caused it? She wasn’t surprised to learn of my grief: “Genes load the gun.
Environment pulls the trigger.” Thyroid problems do run in my family: my grandmother was diagnosed with an overactive thyroid at 38, after losing a lot of weight very quickly (a symptom I didn’t have).
However, as I discovered, getting a diagnosis is not straightforward. Dr Suhail Hussain spent 20 years as an NHS GP and now works as a private home-visiting GP. He says the NHS does not usually run as many tests to diagnose thyroid problems, but in borderline cases, it’s important to check other markers such as the hormones FT3 and FT4, as well as TSH.
Dr Venkatesh Subramanian, a consultant obstetrician and gynaecologist at The Medical Chambers Kensington, adds that thresholds for underactive thyroid can vary across health systems: “TSH levels are not standardised across Europe.”
Symptoms matter as much as the numbers, Dr Hussain says. “Brain fog, fatigue, constipation, weight gain, sluggishness, low mood, dry skin, hair falling out.” Even losing the outer third of your eyebrows is “a documented phenomenon” of thyroid disease.
Dr Natalie Getreu, ovarian biologist and co-founder of Hertility, the UK & Ireland’s leading healthcare provider for women, agrees that there are various markers to test for thyroid problems, and results can vary widely. “Reference ranges describe where results fall in a selected group of people. They’re useful, but a result within range still needs to be interpreted alongside symptoms, history and previous results.”
My results have now settled. My sleep, energy and mood have continued to improve. I’ve got the green light to go for egg freezing, and my levothyroxine dose has been halved. I will continue monitoring my TSH; now I know this is so significant.
I still don’t feel I have a tidy answer to what’s been happening in my own body this year. What I do know is what it costs to get this far: months of educating myself, further private treatment, and pushing for more tests while feeling unwell.
If I hadn’t begun the egg freezing process, with thyroid tests as part of it, I could still be suffering. It appears to have been caught and adjusted early, which is important.
If you’re in my position, ask for TSH alongside FT4, FT3 and both antibody tests. The experts I spoke to stressed that a single “in range” result shouldn’t be the end of the conversation – it should be the start.