Medically reviewed by
Dr. Minako Abe, M.D., Board-certified emergency medicine physician researching the relationship between lifestyle and disease onset in relation to the immune system and cancer, Japan
Your hair, skin, and nails all have many jobs to protect your body and keep you healthy. Together, they are a part of the integumentary system. They block germs and foreign matter from entering your body, protect you from internal injuries, help control your body temperature, and maintain the water content (moisture) in your body.
Skin
Your skin is an endocrine organ that produces hormones while also repairing injuries. It is also your body’s largest organ, making up nearly 15% of an adult’s body weight. The epidermis layer of your skin is vital for skin hydration, and healing cuts and wounds. Skin varies in thickness around the body, with the eyelids being the thinnest and the soles of the feet being the thickest. The skin prevents infection, controls the loss of water and nutrients, and prevents harmful substances from pollution and UV rays from entering the body.
Skin is important for thermoregulation (regulating the body’s temperature). Accessory structures called sweat glands secrete water, salt, and other substances and help the body cool down. When it gets cold, arterioles in the skin will constrict to minimize the amount of heat that is lost. It also plays a significant role in our immune system as there are both innate and adaptive immune mechanisms like macrophages, natural killer cells, antimicrobial peptides, mast cells, and CD8+ T cells that respond to microbial changes within or under the epidermis layer of skin. Overall, the skin has an important function as a physical and chemical barrier against bacteria, fungi, and pathogens.
Hair
Hair or hair follicles also play a role in the body’s ability to heal injuries while also influencing angiogenesis (the formation of new blood vessels) and neurogenesis (the formation of neurons). Surprisingly, hair follicles also house stem cells which are useful for clinical trials to develop treatments for, among other illnesses, chronic ulcers and tendinosis or the degeneration of collagen in a tendon due to overuse. At the base of a hair follicle, there is a bulb where living cells divide and build up the hair shaft. Within the bulb, there are blood vessels that feed the cells and help deliver hormones to control hair growth and structure.
A hair follicle goes through three phases:
- anagen or growth phase
- catagen or transitional phase
- telogen or resting phase
It is during the telogen phase that growth stops and the old hair is pushed out by new hair. Hair has a sensory function where the follicle can sense movement and send information to the central nervous system. For example, if a mosquito were to land on your arm, your hair follicles would sense it and send a message to your brain and spinal cord. This message would trigger you to see the mosquito and swat it away.
Nails
Finally, the nails have several functions including protecting the fingers and toes, helping with scratching, grooming, protection, cosmetic purposes, and improving dexterity.
Nail configuration can tell medical information on a patient’s genetics and lifestyle including malnutrition, disruptions in blood flow, neurogenic factors, and underlying diseases or conditions. Nails can act as a window to systemic diseases. Nail abnormalities can be associated with specific organ diseases like endocrine disease, infectious disease, and pulmonary disease or can be associated with systemic diseases like leukonychia or cardiopulmonary disease.
Therefore, maintaining healthy hair, skin, and nails is essential for not only maintaining your appearance but also for your overall health.
The Thyroid Gland
Your thyroid gland is a hormone gland that plays a role in growth, metabolism, and other bodily functions. The organ is small and located in the front of the neck. It is uniquely butterfly-shaped with two lobes sitting against the windpipe with a narrow strip of tissue.
On average, the thyroid gland weighs between 20 and 60 grams and can move around when we swallow. The gland primarily produces the hormones thyroxine (T4) and triiodothyronine (T3) which can alter the structure of the hair, skin, and nails. The gland is also susceptible to diseases that limit the production of hormones and can negatively impact the quality and health of the entire body.
An underactive thyroid gland causes the patient to have hypothyroidism. An overactive thyroid gland is also known as hyperthyroidism. When the thyroid gland is not functioning properly, it can have a significant impact on hair, skin, and nails.
The Effect of Hypothyroidism on the Integumentary System
Effects on Skin
Hypothyroidism can result in dry skin. This is caused by decreased eccrine gland secretions influenced by the thyroid gland. Thyroid dysfunction can be seen in the skin in three ways:
- Directly affecting thyroid hormones on skin tissue
- Thin, scaly skin
- Edema on the hands, face, or eyelids
- Carotenemia
- Decreased sweating
- Impacting non-skin tissues
- Drooping of upper eyelids
- Cold intolerance
- Hyperpigmentation
- Causing autoimmune skin disease
- Vitiligo
- Eczema
- Connective tissue diseases
- Urticaria
With hypothyroidism, the skin can become rough and scaly as the epidermal layer thins. It also becomes pale and cold due to decreased capillary flow, increased sweating, and thermogenesis (heat dissipation when producing heat). The skin can also become yellow as carotene, an antioxidant, begins to accumulate in the dermis layer. In severely advanced cases, a condition called myxedema may develop, which causes the swelling of the face, lips, eyelids, and tongue, thickened “waxy” skin, multiple organ abnormalities, deterioration of the patient’s mental status, coma, and even death.
Hyperpigmentation of the skin is often seen in patients with Grave’s disease. It is suspected that elevated levels of adrenocorticotropic hormone (ACTH) interact with melanocortin receptors in the skin and induce a change in skin color. Therefore, it is crucial to keep the skin healthy. A healthy diet rich in nutrients such as iodine can also support proper thyroid function and keep the skin smooth and radiant.
Effects on Hair
Hair loss is a common sign of thyroid hormone imbalance. The thyroid hormones help control the rate at which hair follicles grow and fall out. Both hypothyroidism and hyperthyroidism can cause hair loss. Fortunately, when proper treatment is given, the hair can grow back.
Hypothyroidism can cause hair to become dry, thin, and brittle. This is because the thyroid hormones are essential for hair follicle development and maintenance, and with hypothyroidism, the thyroid gland isn’t producing enough hormones to maintain healthy hair. Without thyroid hormones, the body’s metabolic rate slows down and reduces the amount of oxygen and nutrients that are delivered to the living cells in the hair bulb. With thyroid dysfunction, hair on all parts of the body, not just the scalp, is affected including eyebrows and body hair.
Often, patients with hypothyroidism also experience alopecia, madarosis (loss of eyebrows or eyelashes), and diminished facial hair or thinned beards and mustaches. On the other hand, hyperthyroidism or an overactive thyroid gland can also affect hair growth and cause thinning hair. It is hypothesized that this occurs due to increased metabolic activity causing increased hair proliferation. This leads to rapid shedding of hair and thinning of the scalp and hair follicle diameter causing it to become brittle. The increased amount of thyroid hormones speed up the metabolic rate and puts stress on the hair follicles.
Thyroid disorders can also affect the pigmentation and texture of hair. Early graying of the hair can be a sign of autoimmune thyroid disease and thyroid hormone disruption. Other symptoms of thyroid hormone dysfunction include changes in texture, such as coarse or fine hair. Treatment for thyroid disorders would regulate hormone levels and support healthy hair growth. A balanced diet rich in vitamins and minerals can also support healthy hair including vitamin D, vitamin C, iron, and riboflavin.
Effects on Nails
The thyroid gland is responsible for producing hormones that regulate various bodily functions, including nail growth, strength, and thickness. Thyroid hormones play an important role in the development of nails by stimulating growth promoting nail cells to differentiate into specialized structures.
Hypothyroidism can cause brittle and dry nails that may break easily. Additionally, the nails may turn yellowish or have ridges. On the other hand, hyperthyroidism can lead to thin and brittle nails and may be associated with Plummer’s nails or onycholysis where the nail bed and nail body separate. Both hypothyroidism and hyperthyroidism can cause changes in the nail bed.
Thyroid hormones also affect protein synthesis, inhibiting the body’s ability to maintain healthy nails. Thyroid hormones stimulate the production of keratin, a protein used for healing wounds and making up the framework of nails. This results in stronger and thicker nails that are less prone to breakage. Recall that the thyroid hormones regulate blood flow during thermoregulation. The hormones help supply blood to the nail bed, supplying the nail cells with nutrients and oxygen.
Hashimoto’s Disease on the Skin, Hair, and Nails
Skin
Hashimoto’s disease is characterized by the swelling of the eyelids, face, and often the whole body. A patient’s skin is characterized as dry, cool, and rough with the increased production of keratin causing hyperkeratosis.
Keratosis is often seen on the heels of the patient’s foot where the skin becomes brittle and cracks off into scaly white shreds. The skin also takes on a yellowish tinge or could have signs of blue and red marbling when the temperature drops.
Hair
With this disease, the hair becomes dry and thin, shortening over time. It is likely the patient will experience temporary or permanent alopecia.
In women, there is a possibility of seeing hirsutism (male-pattern hair growth) on the upper lip, chin, cheeks, and inner thighs. This is caused by a decrease in globulin production from the thyroid gland. Globulin binds to sex hormones and may alter the balance of male and female hormones.
Nails
Onychoclasis or nail brittleness, and lamellar dystrophy where the nail splits into horizontal layers can occur. The nail plates become extremely fragile and often break off during daily activities. Grooves or depressions in the nail can also occur. These defects are called Beau’s lines. Fortunately, in many cases, taking the right dosage of levothyroxine has helped alleviate or reverse these nail defects.
Key Takeaways
- Your thyroid gland is an endocrine gland that plays a role in growth, metabolism, and other bodily functions.
- Hypothyroidism can result in dry, rough, cool skin caused by decreased eccrine gland secretions influenced by the thyroid gland.
- Hyperpigmentation of the skin is often seen in patients with Grave’s disease.
- Hair thinning and hair loss are common signs of thyroid hormone imbalance.
- Thyroid hormones are essential for hair follicle development and maintenance.
- Thyroid hormones play an important role in the development of nails by stimulating growth promoting nail cells to differentiate into specialized structures.
