Why do women get more thyroid disease?

▎Women's content team editors have more thyroid dysfunction in women than men, and the incidence increases with age.

This is related to gender differences in immune function.

For example, similar to the causes of many autoimmune diseases, more than 80% of patients with acute or chronic thyroiditis leading to hypothyroidism have anti-thyroid autoantibodies, as well as thyroid B-cell and T-cell infiltration.

At each age, women are twice as likely to carry antibodies against thyroid peroxidase (TPO) as men.

However, in the case of normal thyroid function, TPO antibodies may also exist.
Therefore, there are other factors that can affect the occurrence and development of thyroid dysfunction.

For women, there are some profound physiological changes at different stages of life, which will affect the occurrence of thyroid diseases.

Recently, the Journal of the American Medical Association (JAMA) published a review article.
Two endocrinologists from Johns Hopkins Hospital and the University of Pennsylvania discussed the effects of women’s age, reproduction and pregnancy.
The effect of thyroid function.

Screenshot source: JAMA pregnancy and childbirth and the risk of hypothyroidism In the first trimester, pregnancy will cause the body's demand for thyroid hormones to increase.

This is because placental deiodinase can promote the metabolism of thyroid hormone; at the same time, under the stimulation of estrogen, thyroxine binding globulin (TBG, the main transporter of thyroid hormone) increases; β-human chorionic gonadotropin and stimulating hormone The cross-reaction of thyroid hormone receptors can directly stimulate thyroid cells, thereby achieving an increase in thyroid hormone.

Due to the high TBG level, the total thyroxine level during pregnancy usually rises.

Thyroid-stimulating hormone (TSH) level is the first choice for thyroid function testing during pregnancy.
Elevated TSH indicates the possibility of hypothyroidism.

Women with insufficient thyroid reserves (for example, due to iodine deficiency or autoimmune diseases), may not be able to fully meet their thyroid hormone requirements during pregnancy, leading to an increase in TSH.

Thyroid dysfunction is related to infertility and miscarriage in the first trimester.

Therefore: For women with risk factors for thyroid dysfunction, it is recommended to perform TSH testing before using assisted reproductive technology and during pregnancy.

Women with newly discovered elevated TSH during pregnancy should assess their autoimmunity and treatment needs.

The American Thyroid Association (ATA) proposed that women with TPO antibodies with TSH higher than 4 mIU/L, or women without TPO antibodies with TSH higher than 10 mIU/L, require treatment, and the treatment goal should be lower than 2.
5 mIU/L.

For most women who are already receiving levothyroxine treatment, in order to better meet the needs of pregnancy, the treatment dose needs to be increased in the first three months of pregnancy.

In addition, for women with Graves disease (a type of hyperthyroidism), the dose of antithyroid drugs needs to be reduced during pregnancy and then recovered after delivery.

After childbirth, the incidence of autoimmune diseases in women will also increase (because the immune system will be suppressed to protect the fetus during pregnancy).

5% of women will get thyroiditis after childbirth, and half of them will continue to have hypothyroidism 1 year later.

Image source: 123RF Fertility and abnormal thyroid immunity One phenomenon is that women with infertility and a history of early miscarriage have an increased prevalence of TPO antibodies.

This raises the question: Does abnormal thyroid autoimmunity have a negative impact on reproductive health? Random trials have shown that women with normal thyroid function but with TPO antibodies, thyroid hormone replacement therapy (hypothyroidism) has no effect on pregnancy outcomes.

Therefore, TPO antibodies may indicate an increase in inflammation without directly leading to a poor prognosis of pregnancy.

Menopause: Reduced thyroid hormone demand During the transitional period of menopause, lower estrogen levels will lead to a decrease in TBG, which results in not requiring so much thyroid hormone to maintain free thyroid hormone levels, thereby reducing the demand for thyroid.

However, it is unclear whether this will change the TSH standard.

Fatigue, weight gain, these common symptoms of menopause and hypothyroidism, often drive a large part of TSH testing.

If the free thyroxine level is normal and only TSH is elevated, it is necessary to confirm whether this condition persists before treatment, because the probability of spontaneous increase in TSH is high.

Aging: Elevated thyroid stimulating hormone Even in people without TPO antibodies, TSH levels will increase with age, and the increase in women’s life expectancy further contributes to the slightly increased prevalence of TSH in elderly women Higher.

However, this increase in TSH may not indicate thyroid dysfunction.

Even in healthy elderly people, the increase in TSH may reflect the adaptation of the hypothalamus and pituitary gland to chronic inflammation or circadian rhythm changes.

Observational data show that the TSH level is between 4.
5mIU/L-7mIU/L and there will be no adverse effects without treatment.

In a randomized trial, thyroid hormone therapy for adults 65 years and older with a median TSH level of 5.
8 mIU/L did not show any symptomatic benefit.

Therefore, before initiating levothyroxine therapy, the degree and persistence of TSH elevation should be considered.

In addition, excessive levothyroxine can increase the risk of arrhythmia and fractures, and data shows that in elderly women, levothyroxine exposure is nearly 5 times that of elderly men, which suggests that more attention should be paid to elderly women taking levothyroxine Happening.

Image source: 123RF summary JAMA article pointed out that for women, the correct understanding and handling of thyroid function is an important health issue.

During pregnancy, this will affect the health of mothers and babies; for non-pregnant women, before receiving thyroid hormone replacement therapy, age and other factors that may reduce thyroid hormones and increase TSH should also be considered.

Understanding the physiological changes throughout the life cycle helps to optimize the management of women's thyroid health.

Related reading "The Lancet" Sub-Journal: The incidence of thyroid cancer in Shanghai and Hangzhou is "far ahead".
How high is the rate of overdiagnosis in various parts of China? The incidence of all major subtypes of thyroid cancer in China is increasing! The International Agency for Research on Cancer published the opinion of an authoritative endocrinologist on global incidence trends: What should I eat to promote thyroid health? What shouldn't you eat? References [1] Mammen JSR, Cappola AR.
(2021).
Autoimmune Thyroid Disease in Women.
JAMA, doi:10.
1001/jama.
2020.
22196 Note: This article aims to introduce the progress of medical and health research, not a treatment plan recommendation.

If you need guidance on treatment plans, please go to a regular hospital for treatment.