Itching and Associated Diseases

Itching or pruritus is defined as the skin sensation that prompts the patient to scratch a particular area of the skin. Irritative stimulation of skin is caused due to activation of free nerve endings situated at the dermo-epidermal junction. Itching is a physiologic or pathologic symptom caused due to internal or external factors. Itch receptors present in the free nerve endings at the dermo-epidermal junction are stimulated by histamine and other anaphylactic substances and evoke motor response of scratching. If not controlled, scratching may lead to skin injury and infection. There is a scratching itch cycle and one feels relieved after the itching cycle. Itching or pruritus is the most common disease of the skin caused by innumerable causes. If the cause of itching/pruritus remains undiagnosed even after two weeks then it is labeled as pruritus of undetermined origin (PUO). The cause of itching/pruritus could be local or systemic. It can be associated with the following systemic diseases.

Renal disease and pruritus:

Chronic renal failure (CRF) is a well-recognized cause of generalized and persistent pruritus. Uremia during CRF and cellular changes in the skin could be the possible cause of itching/pruritus. It is not directly related to renal function parameters, as patients with acute renal failure (ARF) do not complain of itching.

Liver disease and pruritus:

Patients with liver disease may also present with mild transient or severe or persistent sensation of itching. Intra-hepatic or extra-hepatic cholestasis in these patients leads to pruritus or itching. Primary billiary cirrhosis, cholangitis, viral infections, drugs and pregnancy can cause intra-hepatic cholestasis and lead pruritus.

Pregnancy and pruritus:

Pregnant women with mild abnormalities of liver function in the form of cholestasis may develop itching in the third trimester of pregnancy. Three out of 100 pregnant women may have pruritus.

Endocrine diseases and pruritus:

Pruritus confined to genital or peri-anal areas is most common in diabetics. Patients with diabetes mellitus sometimes may present with pruritus as the main presenting feature for medical consultation. Patients suffering from hypothyroidism and hyperthyroidism may also have generalized itching or pruritus.

Pruritus in occult malignancies:

Intense itching of nostrils has been observed in patients with tumors of brain. Adenocarcinomas and squamous cell carcinomas of various organs may also lead to generalized itching/pruritus. Around 30% patients with Hodgkin's disease have been found to be affected by itching disorder; some patients may show these symptoms as presenting features.

Signs and Symptoms of Thyroid Disorders

Cretinism

Thyroid gland is associated with the general metabolism of all body tissues. Suboptimal activity of thyroid gland at birth leads to hypo-secretion of thyroid hormones and causes cretinism impairing the mental and physical growth of an infant or child. The child grows up a mentally retarded dwarf, unless diagnosed and treated with thyroid extract. The cretin child has a stunted body with broad face and wide nostrils. The mouth and tongue of a cretin child are so big that the mouth may not be closed properly. The affected child could have protuberant abdomen with an umbilical hernia. The child is very sluggish and cannot be taught to walk, talk and personal hygiene tips.

Hypothyroidism

Patients affected by under function of thyroid gland or hypothyroidism, develop generalized oedema called myxoedema (swelling of body). In myxoedema metabolic processes slow down with a tendency to gain weight. There is slowness of mind and speech and one feels lethargic. The skin becomes thickened and dry. The body temperature is subnormal, pulse slow and hair may fall or get thin. Treatment of hypothyroidism needs thyroid hormone as oral drugs. Pro-thyroid drugs used for treatment of hypothyroidism, increase the metabolic rate with a subsequent increase in catabolism. Self-medication of hypothyroidism is not advisable.

Hyperthyroidism

Enlargement of thyroid gland with increased secretion is termed as hyperthyroidism. In hyperthyroidism the metabolic rate is increased and the body temperature may be higher than the normal with very fast pulse rate. The patient loses weight and is nervous and excitable. The cardiac output is generally increased and cardio-vascular complications like fibrillation may develop if hyperthyroidism is not treated effectively and timely. However, enlarged thyroid gland could be associated with non-toxic or toxic goitre. Goitrous gland may have normal function or under function (hypothyroidism) or over function (hyperthyroidism). The exophthalmic goitre is known as Graves's disease and in this disease the eyeballs protrude. The effect is due to over activity of thyroid hormone and may not completely be reversed with treatment. The hyperthyroidism is treatable with anti-thyroid drugs but self-medication is not advisable as it could be harmful if other ailments like diabetes, cardiac problem or coagulopathies exist. Sometimes surgical removal of thyroid gland is also advised for the treatment of hyperthyroidism and thyrotoxicosis or the thyroid gland is bombarded with x-ray like radiations from radioactive iodine accumulated in the gland after it had administered to the patient.

Thyroid Gland and its Functions

Thyroid Gland and its Secretions

Thyroid is an endocrine gland situated in the front of neck. It consists of two lobes, lying one on each side of the trachea just below the larynx. Both the lobes are joined by narrow band of thyroid tissue called isthmus of thyroid. The gland receives very rich supply of blood and consists of a large number of vesicles formed by secreting cells grouped around the small cavities called alveoli. The thyroid alveoli contain very thick colloid or gummy substance, composed of thyroxine hormone, which is rich in iodine content. Secreting cells of the vesicles contain an internal secretion known as thyroglobulin which is broken down to thyroxine and released in the alveoli of thyroid. The thyroid gland governs the general metabolism of all body tissues. The triiodothyronine (T3) hormone is also present in the colloid of thyroid gland and blood plasma. The triiodothyronine (T3) has been found to be more active than thyroxine. Thyroxine is an iodine derivative of thyronine. Thyroxine has four iodine atoms in its molecule and could also be called T4 hormone. The function of thyroid is regulated by thyrotrophic hormone of the anterior lobe of pituitary gland. Normally thyroid is not palpable but may get enlarged where there is deficiency of iodine in water supply. Enlarged thyroid could be associated with non-toxic or toxic goitre. Goitrous gland may have normal function or under function (hypothyroidism) or over function (hyperthyroidism). Suboptimal activity of thyroid gland at birth leads to hypo-secretion of thyroid hormones and causes cretinism. Cretinism is a disorder of thyroid in which mental and physical growth are retarded.

Functions of Thyroid Gland

The thyroid gland controls the body metabolism in terms of temperature, pulse rate, respiratory rate, cardiac output, appetite, body weight, emotions, nervous temperament and intelligence. Though it looks strange to put the emotions, nervous temperament and intelligence under the metabolic functions but it is true that the metabolic changes influence all these. Thyroid gland and its iodine containing hormones play a vital role in metabolic processes of our body essential for good health.