Introduction

Causes of hyperthyroidism in females are a common concern that I encounter in my daily clinical practice. Many women come to the clinic worried about sudden weight loss, palpitations, mood swings, or menstrual irregularities. After careful evaluation, they are often surprised to learn that these symptoms are linked to an overactive thyroid gland.

Although hyperthyroidism(overactive thyroid) can affect both sexes, research shows that it is five to ten times more common in women. It is caused by a combination of genetic predisposition, hormonal fluctuations, and unique life stages such as pregnancy and menopause.

In this article, I will tell you about the causes of hyperthyroidism in women with the help of research, clinical insights, and patient experiences. You will also discover some rarely discussed triggers that most health blogs miss, which will help you understand this condition clearly.

What are the causes of hyperthyroidism in women?

The main causes of hyperthyroidism in women include Graves’ disease (spontaneous overactivity of the thyroid), toxic thyroid nodules, thyroiditis (inflammation), excessive iodine intake, drug related effects (for example, amiodarone), and hormonal changes during pregnancy or postpartum. Rarer causes include pituitary adenomas and certain tumors that stimulate thyroid hormone production. Women are more vulnerable due to hormonal fluctuations (estrogen, pregnancy, menopause) and genetic predisposition. Early recognition of these causes is crucial to prevent complications such as irregular heart rhythms, osteoporosis, and thyroid storm.

Understanding Hyperthyroidism(Overactive Thyroid) in Women

Hyperthyroidism(overactive thyroid) occurs when the thyroid gland produces too much thyroxine (T4) and triiodothyronine (T3), hormones that regulate metabolism.

Why are women more affected?

• Autoimmunity: Women are much more likely to develop autoimmune diseases about 80% of autoimmune patients are women (PubMed, 2022).
• Hormonal changes: Estrogen and progesterone affect the sensitivity of the immune system, which can trigger autoimmune thyroiditis.
• Life stages: Pregnancy, postpartum recovery, and menopause increase the risk of thyroiditis.
• Global data: According to the World Health Organization (WHO), thyroid disorders affect 200 million people worldwide, and women are disproportionately affected.

1. Causes of Hyperthyroidism in Females: Genetic Factors

One of the most important yet sometimes under-discussed contributors is genetics.

• Family history: If a mother or sister has thyroid disease, the risk increases significantly.
• HLA gene variants: Certain immune system genes (for example, HLA-DR3) are strongly linked to autoimmune thyroid disease.
• Twin studies: Research suggests that there is a 30-60% genetic contribution to Graves’ disease and autoimmune hyperthyroidism.

Doctor’s insight: I often see young women in my practice who have no lifestyle risk factors but a strong family history of thyroid disease. When one sister develops Graves’ disease, the other often follows within a few years.

2. Causes of Hyperthyroidism in Females: Graves’ Disease

Graves’ disease is the most common cause of hyperthyroidism in women, accounting for about 60-80% of cases (Mayo Clinic).

Mechanism

The immune system produces thyroid-stimulating immunoglobulins (TSI), which bind to thyroid receptors and increase hormone production.

Risk in women

• Women aged 20-40 are most affected.
• Emotional stress and pregnancy can act as triggers.

Symptoms

• Weight loss despite a normal diet.
• Bulging eyes (exophthalmos).
• Rapid heartbeat and tremors.

Unique insight: Many women experience early symptoms anxiety, heat intolerance, or light periods that are often mistaken for stress or hormonal imbalances. Early thyroid screening is essential.

3. Causes of Hyperthyroidism in Females: Thyroid Nodules

Nodules are lumps in the thyroid that can produce excess hormones.

Types

• Toxic multinodular goiter (Pulmer’s disease): Multiple overactive nodules.
• Toxic adenoma: A single nodule that autonomously secretes thyroid hormones.

Gender relationship

Nodules are four times more common in women, especially after age 50. Estrogen can promote nodule growth.

Case example: I once treated a 55-year-old woman who had had mild palpitations for years. Her scan revealed multiple nodules, one of which was hyperfunctioning. After treatment, her symptoms improved dramatically.

4. Causes of Hyperthyroidism in Females: Thyroiditis

Thyroiditis refers to inflammation of the thyroid gland, which can temporarily cause hormone secretion.

Types that affect women

• Postpartum thyroiditis: Affects 5-10% of women within the first year after childbirth.
• Subacute thyroiditis: Often viral, causing painful swelling.
• Silent thyroiditis: Spontaneous, painless, and more common in middle aged women.

Storytelling Insight: A new mother came to my clinic exhausted and worried, convinced she had postpartum depression. Labs revealed hyperthyroidism due to postpartum thyroiditis something that is often overlooked in women after childbirth.

5. Causes of Hyperthyroidism in Females: Medications and Iodine Exposure

Some medications and excess iodine can cause thyroid enlargement.

• Amiodarone-induced thyrotoxicosis: Seen in patients taking heart medication.
• Iodine contrast agents: Used in imaging, can trigger hyperthyroidism in susceptible women.
• Excessive supplements: Some women take unregulated “thyroid boosters” or seaweed-based supplements that contain high levels of iodine.

WHO data: The safe daily intake of iodine for adults is 150 mcg, but consuming more than 1100 mcg per day can cause thyroid dysfunction.

6. Causes of Hyperthyroidism in Females: Pregnancy and Postpartum Changes

Pregnancy presents a unique endocrine challenge.

• hCG mimics the hormone TSH and can temporarily increase thyroid activity, especially in the first trimester.
• Postpartum immune reconstitution increases the risk of thyroiditis.
• Hyperemesis gravidarum (severe nausea/vomiting) is associated with transient hyperthyroidism caused by high hCG.

 For detailed guidance: See Treatment of Hyperthyroidism in Pregnancy

Doctor’s Note: I always advise postpartum women to watch for thyroid-related symptoms such as mood swings, fatigue, and hair loss. This is often blamed on “new mom stress” but may actually be a thyroid condition.

7. Causes of Hyperthyroidism in Females: Pituitary Adenomas

Pituitary adenomas are a rare but important cause of hyperthyroidism in women. These tumors grow in the pituitary gland and secrete excess thyroid-stimulating hormone (TSH), which over stimulates the thyroid gland.

Key points:

• Unlike Graves’ disease or nodules, the problem originates in the brain, not the thyroid.
• Women may experience symptoms of both hyperthyroidism and pituitary mass effects, such as headaches or vision problems.
• Diagnosis often requires MRI imaging and special blood tests that show a high TSH with a high T4/T3, which is unusual in regular hyperthyroidism.

Doctor’s insight: I have seen patients misdiagnosed for years because their high TSH was not normal. Awareness of pituitary adenomas is crucial in abnormal thyroid lab results.

8. Causes of Hyperthyroidism in Females: Gestational Trophoblastic Tumors

Gestational trophoblastic disease (GTD) includes rare pregnancy related tumors such as hydatidiform mole or choriocarcinoma. These tumors secrete extremely high levels of human chorionic gonadotropin (hCG), a hormone that can mimic TSH and cause the thyroid to enlarge.

Why it’s important in women:

• Women of reproductive age are at unique risk.
• Symptoms can include severe nausea, vomiting, rapid heartbeat, and weight loss often mistaken for pregnancy complications.
• Blood tests clearly show high hCG levels, and ultrasound confirms the diagnosis.

WHO data: GTD occurs in about 1 in 1,000 pregnancies worldwide, with higher rates in Asia.

9. Causes of Hyperthyroidism in Females: Ovarian Teratomas (Struma Ovarii)

Struma Ovarii is a rare ovarian tumor that contains thyroid tissue, which can independently produce thyroid hormones. It accounts for less than 1% of ovarian tumors, but when present, it can cause clinically significant hyperthyroidism.

Clinical Insight:

• Most cases occur in women aged 40-60 years.
• Symptoms often mimic hyperthyroidism, but thyroid scans may show low uptake in the neck because the source of the hormone is in the ovaries, not the thyroid.
• Diagnosis often requires pelvic imaging and surgical confirmation.

Unique Note: This is a condition that many doctors and blogs overlook. In cases of unexplained hyperthyroidism with abnormal scans, struma ovary should be considered.

10. Causes of Hyperthyroidism in Females: Excessive Iodine

Excessive iodine intake is a well documented cause of hyperthyroidism in women, especially in areas where iodine supplementation is common.

Sources of additional iodine:

• Seaweed supplements (kelp, nori, wakame).
• Iodine rich medications (e.g., amiodarone).
• Contrast dyes used in CT scans and angiography.
• Why are women more likely to be affected?
• Women are more likely to use dietary supplements marketed for “thyroid health.”
• Pregnancy and breastfeeding increase iodine needs, but excessive intake can tip the balance toward overactivity.

CDC Guidance: The safe upper limit of iodine intake for adults is 1,100 mcg per day. Continuing to exceed this amount increases the risk of thyroid dysfunction.

Complications and why early diagnosis is important.

If left untreated, hyperthyroidism(overactive thyroid) in women can cause:

• Irregular menstrual periods and infertility.
• Osteoporosis: Women with hyperthyroidism lose bone mass faster than men.
• Cardiac arrhythmias: Women are three times more likely to develop atrial fibrillation.
• Thyroid storm: A life-threatening emergency.

Read In Detail About: See Symptoms of hyperthyroidism in females ,for early warning signs.

Read In Detail About: Best Diet plan for Hyperthyroidism .

Conclusion and Call to Action

Hyperthyroidism(overactive thyroid) in women is not just a “thyroid problem” it is a condition shaped by hormones, genetics, pregnancy, autoimmune disease and lifestyle factors. Understanding these causes helps women seek timely care and avoid serious complications.

As a physician, I have seen how delayed recognition can affect women’s fertility, bone health and heart health. But with awareness and proper treatment, most women achieve full health and energy.

If you found this article helpful, I would love to hear from you. Share your experiences, ask questions in the comments, or book a consultation if you are concerned about your thyroid symptoms. Your thyroid health matters and early action makes all the difference.

References:

PubMed: Autoimmune and Thyroid Disease in Women

CDC: Thyroid Disease Data

FAQS

🧑‍⚕️ About the Author

 Dr. Asif, MBBS, MHPE

Dr. Asif is a medical doctor and medical educationist with expertise in simplifying complex health topics for the general public. With a passion for preventive health and evidence-based writing, he helps readers make informed choices about their well-being.

✅ Medically Reviewed By

Dr. T.G., MBBS, FCPS (Endocrinology)

Associate Professor, Endocrinology Ward, HMC Hospital

With over 20 years of clinical experience in managing endocrine disorders, Dr. T.G. ensures that the content is accurate, reliable, and clinically relevant.

⚠️ Medical Disclaimer

This blog is intended for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard or delay medical advice based on content you read here.