What the thyroid really does to your weight
Thyroid hormones help set the basal metabolic rate – the energy the body uses at rest. In pronounced hypothyroidism it drops measurably, and the body also retains additional water.
In figures: most women gain a few kilograms from an untreated underactive thyroid, and a substantial part of that is water. Once treatment is properly adjusted, it is usually exactly this share that disappears again – the rest behaves just as it does for everyone else.
At a glance
- Order of magnitude: an untreated underactive thyroid usually accounts for only a few kilograms
- Of which: a large share is retained water, not fat
- Important: levothyroxine is not a slimming aid – overdosing harms the heart and bones
- Easily confused: menopause and hypothyroidism have very similar symptoms
- Clarity: a simple blood test reliably tells the two apart
- Appointment: book online or call us on +43 1 5333 654
Menopause or thyroid?
Exhaustion, sleep problems, mood swings, weight gain, hair loss, irregular bleeding, difficulty concentrating: this list fits both. And both typically begin in the same phase of life.
That is why, in women around fifty with symptoms like these, we always check the thyroid values as well before everything is put down to the menopause. Quite often both are present at the same time – in which case we treat both.
What points to which
| Symptom | more likely menopause | more likely hypothyroidism |
|---|---|---|
| Hot flushes, sweating | typical | atypical – more likely feeling cold |
| Sensitivity to cold | atypical | typical |
| Dry skin | possible | typical, often also cool and doughy |
| Constipation | less typical | typical |
| Changes in the cycle | typical, usually becoming less frequent | typical, often heavier and longer |
| Sleep problems | typical | possible |
This comparison is a guide, not a diagnosis. Only a blood test gives certainty.
And if the values are fine?
Then that is not a consolation prize but useful information: it is not the thyroid. One possible cause is ruled out, and we can keep looking in a targeted way – at the menopause, at iron or vitamin D status, at sleep, at the pressures you are under.
Because gynaecology, internal medicine and nutritional counselling are all under one roof at Woman & Health, this next step does not have to mean a new search for a practice.
Frequently asked questions
I take levothyroxine and am still gaining weight. Is my dose wrong?
If TSH and fT4 are within the target range, the dose is right – and in that case the weight gain is very probably not the thyroid. Increasing the dose would not help here; it would do harm.
Does a “thyroid cure” help with weight loss?
No. Products that market thyroid hormones or high-dose iodine for weight loss are medically indefensible and carry real risks for the heart and bones.
Does hormone therapy during the menopause affect the thyroid?
Oestrogen therapy can increase the need for levothyroxine because more binding protein is produced. If you start or stop hormone therapy, we therefore re-check the thyroid values a few weeks later.