Why And How Females Are More Affected By Thyroid Disease - Dr Manoj Chaddha

Multiple epidemiological studies from India and abroad have shown that females are significantly more affected by thyroid disease than males. The ratio could vary between 6-8:1. Several factors contribute to this gender disparity, including autoimmune predispositions, hormonal differences and genetic factors.

Autoimmune Predispositions

Females have a higher predisposition to autoimmune diseases, which is a major factor in the prevalence of thyroid disorders such as Hashimoto's thyroiditis (leading to hypothyroidism) and Graves' disease (leading to hyperthyroidism).

In autoimmune thyroid diseases, the immune system (WBC) mistakenly attacks the thyroid gland, leading to its dysfunction.

In addition, certain genetic markers associated with autoimmunity are more commonly found in females. These genetic predispositions (discussed subsequently) increase the likelihood of developing autoimmune thyroid diseases.

Hormonal Differences

One of the most prominent reasons females are more affected by thyroid disease is the influence of female sex hormones, particularly estrogen and progesterone. The menstrual cycle and pregnancy do cause significant hormonal shifts.

During pregnancy, there is an increased demand for thyroid hormones to support fetal development. This could increase the incidence of thyroid disease in susceptible women.

Autoimmune diseases are known to be exacerbated during the first half of pregnancy. They seem to get controlled in the later half and flare up after delivery.

Postpartum thyroiditis, an inflammation of the thyroid gland, can affect 9-11% women after childbirth. This condition is often missed out as the features are very similar to post-partum blues. A large majority of these women go into remission over the next 6-9 months of follow-up.

The incidence and prevalence of Subclinical hypothyroidism increases during the peri-menopausal period. It may be triggered by the decline in estrogen levels and weight gain seen after menopause.

Genetic and Epigenetic Factors

Genetic and epigenetic factors play a significant role in the higher prevalence of thyroid disease among females. The chromosomal make-up of females is 46 XX (whereas males are 46 XY).

Multiple studies have identified genes that are associated with an increased risk of thyroid diseases. Many of these genes are located on the X chromosome. The presence of two X chromosomes can lead to a higher likelihood of expressing these genes that then predispose them to thyroid dysfunction.

Environmental factors such as stress, diet, and exposure to toxins can cause epigenetic changes that affect gene expression. These changes can trigger or exacerbate thyroid diseases, and females may be more sensitive to such epigenetic modifications due to hormonal and genetic differences.