Dr TABASUM SALIM MB BS
21/01/2021
THYROID FUNCTION AND HAIR STATUS
Diseases of the thyroid predominantly affect females and are common, occurring in about 5% of the population. The thyroid axis is involved in the regulation of cellular differentiation and metabolism in virtually all nucleated cells, so that disorders of thyroid function have diverse manifestations. Structural diseases of the thyroid gland such as goitre, commonly occur in patients with normal thyroid function.
Thyroid conditions occur when your thyroid gland either doesn’t produce enough or produces too much of certain hormones. Hypothyroidism, or underactive thyroid, can cause many symptoms, from weight gain to fatigue. Many people don’t develop symptoms of hypothyroidism until months or years have passed because it develops slowly. Hyperthyroidism, overactive thyroid, may cause anything from weight loss to nervousness. Both conditions can cause dry, brittle hair or thinning hair on your scalp and body.
Severe and prolonged hypothyroidism and hyperthyroidism can cause loss of hair. The loss is diffuse and involves the entire scalp rather than discrete areas. The hair appears uniformly sparse. Regrowth is usual with successful treatment of the thyroid disorder, though it will take several months and may be incomplete. It is unusual for mild (e.g. subclinical) hypothyroidism or hyperthyroidism, or short-lived thyroid problems to cause hair loss. Some forms of hypothyroidism and hyperthyroidism come on abruptly and are diagnosed early, while others may have been present for months or years before diagnosis. Hair loss due to thyroid disease becomes apparent several months after the onset of thyroid disease. This is due to the long hair cycle. In such cases, paradoxically the hair loss may follow the treatment for the thyroid and the thyroid medication may be erroneously blamed, leading to withdrawal of treatment, which in turn may worsen the hair loss.
Epidermal thickness is reduced in patients with hypothyroidism and the rates of epidermal cell division and anabolic activity in the epidermis are increased in thyrotoxicosis (Holt et al. 1976). The changes observed in both hypothyroidism and hyperthyroidism states are reversible when the euthyroid state is restored. Epidermal receptors for thyroid hormone appear to be specific for tri-iodothy-ronine (Holt and Marks 1977).
HYPOTHYROIDISM:
Hypothyroidism is a common condition with various causes, commonly autoimmune, iatrogenic, congenital or due to iodine deficiency. Women are affected approximately six times more than men.
The clinical presentation depends on the duration and severity of the hypothyroidism. Those in whom complete thyroid failure has developed over months or years may present with a variety of clinical features. A consequence of prolonged hypothyroidism is the infiltration of many body tissues by the mucoplysaccharides hyaluronic acid and chondroitin sulphate, resulting in a low- pitched voice, poor hearing, slurred speech due to a large tongue and compression of the median nerve at the wrist (carpel tunnel syndrome), infiltration of the dermis gives rise to non-pitting edema (myxoedema) which is most marked in the skin of the hands, feet and eyelids/ the resultant periorbital puffiness is often striking and may be combined with facial pallor due to vasoconstriction and anaemia, or a lemon-yellow tint to the skin caused by carotenaemia, along with purplish lips and malar flush.
In severe hypothyroidism of long duration, the skin appendages are almost absent (Berkheiser 1955). When the changes are rather less severe (Saito et al. 1976) the number of appendages in the atrophic epidermis is reduced and horny plugs are seen in orifices of sweat ducts and follicles.
There is no consistent correlation between the degree and duration of hypothyroidism and the severity of alopecia, mostly because the thyroid, apart from its direct effect on the hair cycle has other metabolic activities which can directly or indirectly affect hair growth (Saito et al. 1976). While a dry skin and diffuse sparsity of scalp and body hair are commonly seen in cretins (Butterworth 1954) and in myxoedema, diffuse alopecia may be the only cutaneous sign of hypothyroidism (church 1965). The cases of hypothyroid alopecia must likely to come to the notice of the dermatologist are cases of this type, including those in whom hypothyroidism has been induced by antithyroid drugs or by iodides (Chapman and Main 1967).
The alopecia in hypothyroidism is of very gradual onset and is diffuse. The microscopy of plucked hairs shows a marked increase in the proportion in telogen. The telogen ratio drops rapidly when thyroxin is administered and resting follicles re-enter anagen (Freinkel and Frienkel 1972). The routine history taken from the patient with diffuse hair loss without obvious cause, should include questions concerning gain in weight, cold tolerance and energy and initiative. Even in the absence of symptoms of hypothyroidism the serum protein-bound iodine and the thyroid radio-iodine uptake and the blood thyroxin level should be estimated.
An unusual clinical manifestation of hypothyroidism is myxoedema of the scalp, presenting as diffuse thickening with the consistency ‘of a rubber pillow’ (Frankel and Frankel 1964). The scalp hair was normal. The diagnosis was confirmed histologically and biochemically.
Hypothyroid alopecia responds promptly to replacement therapy with thyroxin, unless it is of very long duration and some follicles have atrophied. However, alopecia in a patient who is biochemically hypothyroid is not necessarily wholly or even partly the result of impaired thyroid function. We have frequently seen patients with common baldness who have been treated for long periods with thyroxin on the basis of borderline biochemical findings, or even of a so-called ‘clinical diagnosis’ of hypothyroidism based on gain in weight and perhaps on elevated serum cholesterol level, neither of which is an acceptable diagnostic criterion.
THYROTOXICOSIS:
Thyrotoxicosis describes a constellation of clinical features arising from elevated circulating levels of thyroid hormone. The most common causes are graves disease, multinodular goitre and autonomously functioning thyroid nodules (toxic adenoma). Thyroiditis is more common in parts of the world where relevant viral infections occur, such as north America.
The most common symptoms are weight loss with a normal or increased appetite, heat intolerance, palpitations, tremor and irritability. Tachycardia, palmar erythema and lid lag are common signs. All causes of thyrotoxicosis can cause lid retraction and lid lag, due to due to potentiation of sympathetic innervation of the levator palpebrae muscles, but only graves disease causes other features of opthalmopathy, including periorbital oedema, conjunctival irritation, exophthalmos and diplopia. Pretibial myxoedema and the rare thyroid acropachy (a periosteal hypertrophy, indistinguishable from finger clubbing) are also specific to graves disease.
Severe thyrotoxicosis is said to cause diffuse alopecia of the scalp. There are not many cases in which this cause for the hair loss could be established beyond doubt. Nor can it be confirmed that decreased axillary hair is a feature of about 50% of thyrotoxicosis. Most people with hypo- or hyper-thyroidism have autoimmune thyroid disease. If a person has one autoimmune disease, he/she is more likely than others to develop some other autoimmune condition. Alopecia areata is an autoimmune condition that causes hair loss that occurs in people with autoimmune thyroid disease more often than expected by chance. Unlike the types of diffuse hair loss described above, alopecia areata causes discrete, often circular, areas of hair loss. In most cases this is transient and does not progress, but unfortunately it can cause significant baldness. There are other rare autoimmune conditions that can cause hair loss through scarring (e.g. lupus erythematosus), which are associated with autoimmune thyroid diseases. Polycystic ovarian syndrome is also associated with autoimmune thyroid disease and may manifest as diffuse hair loss; other features are irregular periods, obesity and acne.
HAIR LOSS AND ANTI-THYROID TREATMENT:
Anti-thyroid drugs (carbimazole and propylthiouracil) can, in rare cases, cause diffuse hair loss. It may be very difficult to tell whether the hair loss is due to the effects of the previous overactivity of the thyroid or the anti-thyroid drugs. In all probability the anti-thyroid drugs are not the cause and it is unusual to have to seek alternative treatment for hyperthyroidism. Radioiodine does not cause hair loss.
MANAGEMENT:
If you are already a known case of a thyroid disorder, then your doctor may suspect that as the cause of your hair fall. But in case you have not been previously diagnosed with thyroid disease or another autoimmune condition, your doctor may advise you to take some tests typically used to diagnose underlying diseases. The first line investigations are T3, T4 and TSH. The combination of negligible iodine uptake, high T3:T4 ratio or undetectable thyroglobulin is diagnostic. More tests can be done to rule out hormonal imbalances, nutritional deficiencies and medication side effects. The most common tests to be done are for haemoglobin and vitamin D, along with a full thyroid profile.
Definitive treatment of thyroid disorders include taking anti-thyroid drugs, which can be lifelong. In severe cases of thyrotoxicosis, radioactive iodine and surgery maybe needed. Medication includes a non-selective B-adrenoreceptor such as propranolol or nadolol. Beta- blockers however should not be used long term, but provide excellent results when used short term. These medications should only be prescribed by a proper endocrinologist. In most cases, getting your thyroid hormones adjusted will reverse the hair loss, though it may take several months for the hair to grow back.
Along with the anti- thyroid medication, a trichologist prescribes medications and various treatments in order to stop the hair-fall. Patient is counselled, and is explained that the hair-fall is not permanent and can be managed. Patient can be started on biotins and vitamins. A healthy diet is advised. Medication such as minoxidil is given. Avoid brushing your hair excessively, using harsh colouring products, and hairstyles that pull on the hair (such as a tight bun). If the patient feels self-conscious about having thin hair or bald patches, advice wearing a scarf or wig while the hair grows back.
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