The normal thyroid gland consists of two lobes joined by an isthmus in the middle. Thyroid gland is located in the front of your neck. The thyroid gland synthesizes two hormones, T3 and T4, from iodine taken in the diet. Production of T3 and T4 in the thyroid is controlled by a mechanism called feedback mechanism. T3 is the metabolic active hormone which acts as a stimulus. Thyroid hormones control the general metabolism by regulating the rate of oxidation and production of energy. They maintain the basal metabolic rate of the body. They promote growth of body tissues and development of mental functions during infancy and childhood.
A clinical condition caused by low levels of circulating thyroid hormones is called hypothyroidism. It is called primary when the cause of it lies in the thyroid itself. It becomes secondary when hypothyroidism occurs due to the disease of anterior pituitary or hypothalamus. Goitrous hypothyroidism is associated with enlargement of thyroid. Primary hypothyroidism is more common than secondary.
- Idiopathic or spontaneous or atrophic hypothyroidism:- it is an autoimmune disorder mostly occurring in females. There is destruction of thyroid follicles by autoimmune process leading to atrophy of thyroid. Patient of Graves disease treated with Antithyroid drugs develop spontaneous hypothyroidism at a variable period of 10-20 years.
- Hashimoto’s thyroiditis:-it is a common cause of goiter with hypothyroidism. It is an autoimmune disorder. It has slow insidious onset. It affects mostly females in the age group of 30-50 years. The thyroid is diffusely enlarged, occupies major portion of neck. It may be associated with other autoimmune disorders.
- Deficiency of Iodine:- This occurs in persons living in hilly areas such as Himalayas, where goiter is seen in more than 10% of population or may occur during puberty
- Drug induced:- Lithium carbonate is an antipsychotic drug used in the treatment of manic depressive psychosis. It produces asymptomatic goiter
- postablative:- it follows post-ablative surgery or radioactive treatment for thyrotoxicosis. It does not require treatment as patients are asymptomatic and disease is self-limiting
- maternally transmitted
- over treatment by antithyroid
Symptoms depend on the age at which deficiency manifests duration and severity of the disease. Infantile hypothyroidism is seen in the infants (age less than 1 year). The symptoms are mental retardation, delayed milestones of development, pot belly, protruding tongue, flat nose, dry skin and sparse hairs. This condition is called cretinism. X-ray of bone shows delayed bone age. This should be promptly treated; otherwise, mental deficiency will persist.
Juvenile hypothyroidism manifests at adolescence and is characterized by short stature, retarded growth, and poor performance at school, delayed puberty and sexual maturation. Other features of adult hypothyroidism are present to variable degree.
The clinical picture of adult hypothyroidism is nonspecific and insidious in onset. The symptoms and signs are due to slow metabolic rate and due to deposition of mucopolysaccharides into various body tissues such as larynx causing hoarseness of voice, deafness, tongue producing slurred speech, skin with non-pitting edema, puffiness of face, hands, feet and eyelids. It is called as myxedema because of characteristic infiltration of skin by myxomatous tissue. There may be symptoms of compression of long nerves.
Symptoms and signs of adult hypothyroidism
- General features:-tiredness, weight gain, cold intolerance, hoarseness of voice and lethargy are common.
- Cardiovascular:-slow pulse rate, hypertension and xanthelasma are common. Precipitation of angina and cardiac failure are less common
- Neuromuscular:-aches and pains, delayed relaxation of ankle jerks and muscle stiffness are common. Carpel tunnel syndrome, deafness, psychosis, depression, myotonia are less common
- Hematological:- anemia may be present
- Dermatological:-dry thick skin, sparse hair, non -pitting edema are common
- Reproductive:-menorrhagia, infertility and impotence is less common
- Gastrointestinal:- constipation
What is the Treatment for Hypothyroidism?
Treatment of hypothyroidism is lifelong replacement of thyroid hormones by L-thyroxine; the dose is prescribed as per patient’s need so as to maintain normal metabolic activity. Patients feel better within 2-3 weeks after the start of replacement therapy. First of all, patients feel slightly active, there is decrease in weight. Puffiness of the face disappears. There is noticeable change In voice and bowel evacuation. The changes of skin, hair and effusion take longer time, that is, 3-6 months to disappear.