Introduction

Spring is analogous to allergy season for some people. Although it is the time to relax and enjoy flower fields and sunshine, spring allergies can be a thief of joy for people affected by skin conditions and other allergies. 

Pruritus or itching is a commonly seen skin condition that is uncomfortable and intolerable to the extent that it affects the patient’s quality of life.¹ Pruritus (itchy skin) is the most common symptom of various skin diseases and is uncontrollable in some cases. Pruritus often occurs as a symptom of certain systemic diseases such as metabolic diseases, infection, inflammatory diseases, endocrine diseases, psychiatric conditions, cancer and neurologic disorders.¹ 

This article will explore the relationship between pruritus and thyroid disorders along with diagnostic and condition management options. 

Understanding thyroid disorders

Thyroid disorders can be divided into hypothyroidism and hyperthyroidism, the important terms to be clarified to ensure you are looking at accurate treatment plans as the definition and mechanism of action of both conditions are opposite. The thyroid gland is a small butterfly-shaped gland in the neck, located right in front of the windpipe and functions to produce hormones such as triiodothyronine (T3) and thyroxine or tetraiodothyronine (T4) that are crucial in regulating the metabolic pathway of human bodies.² 

T3, T4, and thyroid-stimulating hormone (TSH) are the key hormones used to diagnose thyroid disorders An adequate feedback mechanism is maintained to achieve homeostasis as TSH from the anterior pituitary gland, thyrotropin-releasing hormone (TRH) from the hypothalamus and T4 work synchronously.³ 

Common thyroid disorders and their overall mechanism are as follows: 

Pruritus: an overview

Pruritus (itchy skin) is one of the many symptoms of skin conditions that increase the tendency to scratch one's skin. Even though some cases can be controlled by taking self-care measures, pruritis can often be intolerable or uncontrollable, leading to a steady decline in the affected people’s quality of life. 

The most common causes of pruritis or itching include:¹ 

1. Dermatological causes such as eczema, contact dermatitis, urticaria, prurigo and neurodermatitis
2. Systemic causes such as inflammatory and metabolic diseases, infections, endocrine disorders including hypothyroidism and hyperthyroidism, cancer, and psychiatric conditions
3. Neurological causes such as post-herpetic neuralgia, which is often brought about by pathological changes in the sensory nerve fiber pathways. Another neurological cause could be potentially derived from the central nervous system without the presence of nerve damage, in which pruritus starts from mediators and receptors transmission

The link between pruritus and thyroid disorders

Thyroid function and disorders are often associated with skin health and lead to conditions such as chronic pruritus. Dry skin, eczema and other skin conditions are very common in people with thyroid function-related autoimmune conditions. 

In autoimmune conditions such as Hashimoto’s disease and Graves’ disease leading to hypothyroidism and hyperthyroidism respectively, the immune system tends to target the thyroid gland and subsequently causes dry, scaly and flaky skin that gets extremely itchy. Moreover, hormonal imbalances caused due to thyroid disorders can also affect skin integrity and sensory nerves, causing uncontrollable itching for affected people. Wrinkly skin and other skin conditions such as eczema and urticaria are also common in people with abnormal thyroid functioning. 

Diagnosis of pruritus in thyroid disorders

The first step to evaluate a case of chronic pruritus (continuous itchy skin) would be to evaluate it clinically and systemically as follows:

Clinical history

The medical history of the patient is looked into first to evaluate any correlation between their clinical history or existing conditions with pruritus (itchy skin). If any doubt arises about the the patient’s itchy skin being a result of an existing or potential medical condition, further tests including blood tests are suggested.

Physical examination

A physician examines the itchy lesions or skin areas that are affected to figure out the root cause of the itching. Other symptoms can also be evaluated during physical examination appointments. Red flags or symptoms of thyroid diseases can be assessed to proceed with a thyroid function blood test to determine T3, T4 and TSH levels in blood. 

Dermatological assessment:

A dermatologist would be able to further physically examine the affected skin areas and delve deeper into the cause of pruritus while also cross-checking the patient’s medical history to conclude the cause and come up with a treatment plan. A skin biopsy might also be suggested by a dermatologist to confirm the diagnosis.⁴

Imaging and other diagnostic tools:

In case of abnormal thyroid function detected in blood test results, imaging tests such as an ultrasound scan can be helpful to visualise nodules in the thyroid gland to diagnose any possible autoimmune thyroid disorder. 

Management of pruritus in thyroid disorders

Tackling the issue from its root is the only solution to solving any medical condition. Treatment of the underlying thyroid condition is the most crucial step in managing all the symptoms and side effects of the condition, including pruritus. This can be achieved by administering adequate dosage of medications (levothyroxine for hypothyroidism and antithyroid drugs such as carbimazole for hyperthyroidism).

If medications do not provide a definitive and long-term reversal of the condition, especially in hyperthyroidism patients, surgical options known as partial or total thyroidectomy are sought after. Another more popular non-invasive treatment mechanism to permanently reverse hyperthyroidism is radioactive iodine therapy. 

Specific treatments for pruritus can also provide temporary relief from itching. This includes:

• Topical treatments such as moisturisers and corticosteroids
• Systemic treatments such as antihistamines and phototherapy
• Integrative and supportive therapies including dietary changes and stress management

FAQs

What is pruritus?

Pruritus, or itching, is an uncomfortable, irritating sensation that compels a person to scratch the affected area. It can occur without visible skin changes or can be associated with a rash, lesions, or other skin conditions.

How can thyroid disorders cause pruritus?

Thyroid disorders can lead to pruritus primarily through changes they cause in the skin. For example, hypothyroidism can lead to dry skin, which is more prone to itching. The mechanism involves decreased sweat and oil gland function due to lower metabolic rates, which dries out the skin.

Can treating thyroid disorders relieve pruritus?

Yes, managing the underlying thyroid disorder can often relieve pruritus. For instance, treating hypothyroidism with thyroid hormone replacement therapy usually helps alleviate the skin dryness and subsequently the itching.

Are there specific treatments for pruritus caused by thyroid disorders?

Treatment focuses on managing the thyroid disorder itself along with symptomatic relief for pruritus. Moisturisers, topical steroids, and antihistamines can be used to provide relief from itching. Addressing the thyroid imbalance is crucial for long-term relief. Maintaining good skin hydration through regular use of moisturisers, avoiding hot showers and harsh soaps, and using a humidifier can help manage skin dryness and pruritus. 

How long does it take for pruritus to resolve after starting treatment for a thyroid disorder?

The time varies depending on the individual and the severity of the thyroid disorder. It may take several weeks to several months for thyroid hormone levels to stabilise and for skin conditions to improve following the initiation of thyroid treatment.

Summary

Itching, known as pruritis, is a common symptom of many skin conditions and can also be a sign of underlying systemic diseases such as metabolic disorders, infections, inflammatory conditions, hormonal imbalances, mental health issues, cancer, and neurological disorders. . It is a common symptom in people with thyroid dysfunctions such as hypothyroidism and hyperthyroidism. 

A clinical history evaluation, physical examination, dermatological examination, blood tests and skin biopsy in some cases are carried out to diagnose pruritus as a side effect of thyroid disorders. Treatment and management of pruritus can be done by tackling the thyroid disorder by taking proper medication to target the type of thyroid disorder or by surgical methods. Pruritus can be managed using topical treatments or medications such as antihistamines that help in controlling itching. 

It is vital to recognise pruritus as a potential indicator of thyroid dysfunction and treat the root cause in a timely and effective manner to improve overall health.