Thyroid Health in Women: Why It Matters and What to Look Out For

What the Thyroid Does

The thyroid produces hormones, mainly thyroxine (T4) and triiodothyronine (T3), that regulate the body's metabolism. Metabolism in this sense doesn't just mean weight. It means the speed at which virtually every cell in the body functions, including the heart, the brain, the digestive system, and the muscles. When thyroid hormone levels are off, the knock-on effects are wide-ranging.

Underactive Thyroid (Hypothyroidism)

This is the more common problem, particularly in women over 40. The thyroid doesn't produce enough hormone, and everything slows down. The symptoms come on gradually, which is part of why they're easy to dismiss or attribute to other things.

Typical symptoms include fatigue that doesn't improve with sleep, weight gain without changes to diet, feeling cold when others are comfortable, constipation, dry skin and hair, hair thinning or loss, and low mood or depression. Cognitive symptoms like brain fog and poor memory are also very common and can be quite distressing.

In women, hypothyroidism can affect menstrual cycles, causing heavier or more irregular periods. It can also make it harder to fall pregnant and increases the risk of complications during pregnancy, which is why thyroid function is something I check when women are trying to conceive or have had pregnancy difficulties.

Overactive Thyroid (Hyperthyroidism)

Here the thyroid produces too much hormone and everything speeds up. People feel anxious, jittery, or wired. The heart races or has palpitations. Sleep is difficult. Weight drops despite a good appetite. There can be tremors in the hands, excessive sweating, and a sensitivity to heat.

The most common cause is Graves' disease, an autoimmune condition where the immune system stimulates the thyroid to overproduce. A thyroid nodule can also be responsible. Hyperthyroidism is less common than hypothyroidism but needs prompt treatment because of the strain it puts on the heart.

Autoimmune Thyroid Disease

Most thyroid problems in women are autoimmune in origin. The immune system mistakenly produces antibodies that either attack the thyroid (Hashimoto's thyroiditis, which leads to hypothyroidism) or stimulate it excessively (Graves' disease). Women are around five to ten times more likely than men to develop autoimmune thyroid conditions, and the reasons aren't fully understood.

If you have another autoimmune condition such as type 1 diabetes, rheumatoid arthritis, or coeliac disease, your risk of thyroid autoimmunity is higher. I'll generally check thyroid function in these patients even without specific symptoms.

How It's Diagnosed

A blood test measuring TSH (thyroid-stimulating hormone) is the standard first step. TSH is produced by the pituitary gland to regulate thyroid output. If the thyroid is underactive, the pituitary produces more TSH to compensate. If it's overactive, TSH drops. The TSH result gives a very reliable picture of thyroid function in most cases.

If TSH is abnormal, I'll check the actual thyroid hormone levels (T4 and sometimes T3) and thyroid antibodies to understand the cause. An ultrasound of the thyroid is useful if there's any swelling or nodules that can be felt.

One nuance worth mentioning: TSH reference ranges are broad, and some women feel unwell with TSH levels that are technically within the normal range. If your symptoms are consistent with thyroid dysfunction and your TSH is at the edges of the range, it's worth a more detailed conversation rather than just being told everything is normal.

Treatment

Hypothyroidism is treated with a daily tablet of levothyroxine, a synthetic version of the thyroid hormone T4. Most people tolerate it well and find that their symptoms gradually resolve over several weeks. The dose is adjusted based on repeat blood tests and how you feel. Once stable, it's usually a long-term medication, though the dose may need adjusting over time, especially around pregnancy and menopause.

Hyperthyroidism has more treatment options including medications that block thyroid hormone production, radioactive iodine therapy, or surgery. The right choice depends on the cause and severity, and I'd refer to an endocrinologist for this.

When to Get Checked

I'd suggest thyroid function testing if you have persistent unexplained fatigue, unexplained weight changes, hair thinning, significant mood changes, irregular periods, or difficulty conceiving. It's also worth checking if you have a family history of thyroid disease, as there's a strong genetic component.

It's a simple blood test, and given how much thyroid dysfunction affects quality of life when undiagnosed, it's well worth ruling out.