Quick answer: an underactive thyroid slows the body down. Common symptoms in women include tiredness, weight gain, feeling cold, dry skin, hair thinning, constipation, heavy or irregular periods and low mood. A simple blood test (TSH) usually confirms it, and daily thyroid hormone tablets treat it effectively.
What the thyroid does
The thyroid is a small gland at the front of the neck. It produces hormones that control your metabolism: how fast your body uses energy, how warm you feel, how quickly your heart beats and how your gut moves. When it makes too little, everything slows down.
Hypothyroidism is more common in women than men, and becomes more common with age. The most frequent cause in areas with enough dietary iodine is Hashimoto’s thyroiditis, an autoimmune condition where the immune system damages the gland.
Common symptoms
| Area | What you may notice |
|---|---|
| Energy | Tiredness, needing more sleep, feeling sluggish |
| Weight | Gradual weight gain, difficulty losing weight |
| Temperature | Feeling cold when others are comfortable |
| Skin and hair | Dry skin, brittle nails, thinning hair, hair loss |
| Digestion | Constipation |
| Periods and fertility | Heavy or irregular periods, trouble conceiving |
| Mood and thinking | Low mood, anxiety, slow thinking, forgetfulness |
| Muscles and joints | Aches, stiffness, cramps |
| Heart | Slow heartbeat |
| Neck and voice | Swelling at the front of the neck (goiter), hoarse voice |
| Face | Puffy face or eyes |
Symptoms come on slowly, so many women blame stress, age, pregnancy, postpartum changes or perimenopause. If several of these have been present for weeks or months, ask for a thyroid test. Read also our guide on the causes of chronic fatigue.
Who is more at risk
- Women, especially after 60 and after pregnancy
- A family history of thyroid disease
- Other autoimmune diseases, such as type 1 diabetes, celiac disease or rheumatoid arthritis
- Previous thyroid surgery or radiation to the neck
- Some medicines, such as lithium and amiodarone
How it’s diagnosed
- TSH (thyroid-stimulating hormone): the first-line test. A high TSH means the pituitary is pushing a sluggish thyroid harder. Normal ranges vary by lab, commonly around 0.4 to 4.0 mIU/L.
- Free T4: measures the thyroid hormone itself. Low free T4 with high TSH confirms overt hypothyroidism.
- Thyroid antibodies (TPO): help identify Hashimoto’s.
Subclinical hypothyroidism means TSH is mildly high but free T4 is normal. Doctors may monitor or treat depending on your symptoms, TSH level, age and plans for pregnancy.
Why it matters beyond tiredness
Untreated hypothyroidism can raise LDL cholesterol and triglycerides, which you can read about in our guides on how to lower cholesterol and what causes high triglycerides. It can also contribute to high blood pressure, fertility problems, and complications in pregnancy. Severe, long-standing cases can become dangerous.
Treatment
Most people take levothyroxine, a synthetic thyroid hormone, once a day. A few practical points:
- Take it on an empty stomach with water, usually 30 to 60 minutes before breakfast, at the same time every day.
- Keep it four hours apart from calcium, iron supplements and antacids, which block absorption.
- Your dose is adjusted by checking TSH about 6 to 8 weeks after a change, then once a year when stable.
- Don’t stop it when you feel better. It is usually a long-term treatment.
- Tell your doctor right away if you become pregnant or plan to, since dose needs often rise.
Weight and energy usually improve gradually over weeks to months once levels are corrected. Levothyroxine is not a weight loss drug, and taking extra can be harmful.
When to see a doctor
Ask for a thyroid test if you have several of these symptoms, a swollen neck, or a family history. Get urgent care if you have severe drowsiness, confusion, very low body temperature or a very slow heartbeat, which can signal a rare emergency called myxedema.
Frequently asked questions
Can hypothyroidism cause hair loss?
Yes. Hair becomes thin and brittle, and it usually regrows after the thyroid level is corrected, though this can take months.
Can you have normal TSH and still have hypothyroidism?
Rarely. If symptoms persist with a normal TSH, doctors check free T4 and look for other causes.
Can diet cure hypothyroidism?
No. A balanced diet supports health, but Hashimoto’s and most other causes need medicine. Don’t take iodine or kelp supplements without advice.
Does hypothyroidism affect pregnancy?
Yes, untreated it can affect fertility and the pregnancy. With treatment and monitoring, most women have healthy pregnancies.
Cura Editorial Team
Contributor at Cura Health Journal.