In hypothyroidism Decreased secretion of thyroid hormones is called hypothyroidism. Hypothyroidism leads to myxedema in adults and cretinism in children.
Myxedema is the hypothyroidism in adults, characterized by generalized edematous appearance.
Causes for Hypothyroidism (myxedema)
Myxedema occurs due to diseases of thyroid gland, genetic disorder or iodine deficiency. In addition, it is also caused by deficiency of thyroid-stimulating hormone or thyrotropin-releasing hormone.
Common cause of myxedema is the autoimmune disease called Hashimoto’s thyroiditis, which is common in late middle-aged women. In most of the patients, it starts with glandular inflammation called thyroiditis caused by autoimmune antibodies. Later it leads to destruction of the glands.
Signs and symptoms of Hypothyroidism
Typical feature of this disorder is an edematous appearance throughout the body. It is associated with the following symptoms:
Swelling of the face
Bagginess under the eyes
3.Non-pitting type of edema, i.e. when pressed, it does not make pits and the edema is hard. It is because of accumulation of proteins with hyaluronic acid and chondroitin sulfate, which form a hard tissue with increased accumulation of fluid
Atherosclerosis: It is the hardening of the walls of arteries because of accumulation of fat deposits and other substances. In myxedema, it occurs because of increased plasma level of cholesterol which leads to deposition of cholesterol on the walls of the arteries.
Atherosclerosis produces arteriosclerosis, which refers to thickening and stiffening of arterial wall Arteriosclerosis causes hypertension. Other general features of hypothyroidism in adults are:
Fatigue and muscular sluggishness
Extreme somnolence with sleeping up to 14 to 16 hours per day
Menorrhagia and polymenorrhea
5.Decreased cardiovascular functions such as reduction in rate and force of contraction of the 6. Increase in body weight heart, cardiac output and blood volume
Increase in body weight
Depressed hair growth
Scaliness of the skin
Frog-like husky voice
Cretinism is the hypothyroidism in children, characterized by stunted growth.
Causes for cretinism
Cretinism occurs due to congenital absence of thyroid gland, genetic disorder or lack of iodine in the diet.
Features of cretinism
A newborn baby with thyroid deficiency may appear normal at the time of birth because thyroxine might have been supplied from mother. But a few weeks after birth, the baby starts developing the signs like sluggish movements and croaking sound while crying. Unless treated immediately, the baby will be mentally retarded permanently.
Skeletal growth is more affected than the soft tissues. So, there is stunted growth with bloated body. The tongue becomes so big that it hangs down with dripping of saliva g of saliva. The big tongue obstructs swallowing and breathing. The tongue produces characteristic guttural breathing that may sometimes choke the baby.
A cretin is different from pituitary dwarf. In cretinism, there is mental retardation and the different parts of the body are disproportionate. Whereas, in dwarfism, the development of nervous system is normal and the parts of the body are proportionate. The reproductive function is affected in cretinism but it may be normal in dwarfism.
Goiter means enlargement of the thyroid gland. It occurs both in hypothyroidism and hyperthyroidism. Goiter in Hyperthyroidism –
Toxic goiter is the enlargement of thyroid gland with increased secretion of thyroid hormones, caused by thyroid tumor.
Goiter in Hypothyroidism – Non-toxic Goiter Non-toxic goiter is the enlargement of thyroid gland without increase in hormone secretion. It is also called hypothyroid goiter. Based on the cause, the non-toxic hypothyroid goiter is classified into two types.
Endemic colloid goiter
Idiopathic non-toxic goiter.
1- Endemic colloid goiter
Endemic colloid goiter is the non-toxic goiter caused by iodine deficiency. It is also called iodine deficiency goiter. lodine deficiency occurs when intake is less than 50 µg/day. Because of lack of iodine, there is no formation of hormones. By feedback mechanism. hypothalamus and anterior pituitary are stimulated. It increases the secretion of TRH and TSH. The TSH then causes the thyroid cells to secrete tremendous amounts of thyroglobulin into the follicle. As there are no hormones to be cleaved, the thyroglobulin remains as it is and gets accumulated in the follicles of the gland. This increases the size of gland.
In certain areas of the world, especially in the Swiss Alps, Andes, Great Lakes region of United States and in India, particu Kashmir Valley, the does contain enough iodine. Therefore, the foodstuffs also do not contain iodine. The endemic colloid goiter was very common in these parts of the world before the introduction of iodized salts.
2-Idiopathic non-toxic goiter
Idiopathic non-toxic goiter is the goiter due to unknown cause. Enlargement of thyroid gland occurs even with out iodine deficiency. The exact cause is not known. It is suggested that it may be due to thyroiditis and deficiency of enzymes such as peroxidase, iodinase and deiodi nase, which are required for thyroid hormone synthesis.
Some foodstuffs contain goiterogenic substances (goitrogens) such as goitrin. These substances contain antithyroid substances like propylthiouracil. Goitrogens suppress the synthesis of thyroid hormones. Therefore, TSH secretion increases, resulting in enlargement of the gland. Such goitrogens are found in vegetables like turnips and cabbages. Soybean also contains some amount of goitrogens.
TREATMENT FOR HYPOTHYROIDISM
The only treatment for hypothyroidism is the administration of thyroid extract or ingestion of pure thyroxine in the form of tablets, orally