Hypothyroidism Cretinism

Myxedema and goiter are the main conditions for which thyroid preparations are indicated. The treatment of cretinism is difficult because it is recognized only at or after birth. Even if this disease could be diagnosed m utero, thyroid hormones do not readily cross the placental barrier. In addition, the fetus, as does a premature infant, rapidly deactivates the thyroid hormones. The halogen-free analogue DlMlT [26384-44-7] (3), which is resistant to fetal deiodinases, may prove useful for fetal hypothyroidism (cretinism). 

Fetus abortion, stillbirth, congenital anomalies, increased perinatal mortality, increased infant mortality, neurological cretinism (mental deficiency, deaf mutism, spastic deplegia, squint), hypothyroid cretinism (mental deficiency), psychomotor defects. 

Table 62.1 Comparative clinical features in neurological and hypothyroid cretinism...

Figure 62.3 A hypothyroid cretin from Sinjiang, China, who is also deaf mute. This condition is completely preventable. On the right is the barefoot doctor of her village. Both are about 35 years of age. Reproduced from Hetzel (1989).

Mentai deficiency, deaf mutism, spastic dipiegia, squint Hypothyroid cretinism ... 

In the same village, a person who was a hypothyroid cretin but was not mentally retarded, felt himself healthy... 

Iodine deficiency affects the socioeconomic development of an afflicted community in other ways than its important physiological manifestations, viz., goiter, hypothyroidism, cretinism, reproductive failure, and child mortality, among others. The socioeconomic retardation of the affected community occurs in two ways. People are mentally slower and less vigorous, so it is harder to educate and motivate them, and thus they are less productive in their work. Besides, iodine deficiency produces more handicapped individuals who depend on others for their care, which in turn diverts the community resources. Secondly, in most of the areas, agriculture is the most important economic activity, and domestic animals suffer from iodine deficiency in much the same way as people do. Therefore, domestic animals are smaller in size and produce less meat, eggs and wool. They also suffer from abortion and are often sterile. 

The unexpected aspect of these neurological findings was that they were as common in currently hypothyroid cretins as they were in euthyroid (neurological) cretins. 

Congenital anomalies Neurological cretinism Mental deficiency, deaf mutism, spastic diplegia, squint Hypothyroid cretinism Mental deficiency, dwarfism, hypothyroidism Psychomotor defects Increased perinatal mortality Neonatal hypothyroidism Retarded mental and physical development Increased infant mortality Retarded mental and physical development... 

This disease is characterized by a decrease or lack of endogenic thyroid hormone secretion. When originating in childhood, it can be clinically described as cretinism (infantile hypothyroidism), and in adults as myxedema (adult hypothyroidism), which is expressed in a loss of mental or physical ability to work, suppression of metabolic processes in the body, and edema. Since thyroid function cannot be restored, the clinical effect is only visible when using thyroid hormones. Using thyroid hormones in hypothyroidism is a replacement therapy that does not correct the disease itself. 

Thyroid deficiency (hypothroidism) has been connected to cretinism and myxedema. Cretinism occurs when hypothyroid children are born intellectually handicapped, are small, and have coarse hair and thick skin. Myxedema, seen in older hypothyroid people, is characterized by subcutaneous semifluid deposits, causing puffiness of the hands and face. The basal metabolism of these patients is depressed to 30 0% below normal, and their body temperature and pulse rate are also reduced. Women suffering from hypothyroidism may give birth to children afflicted with cretinism. 

There are many forms of hypothyroidism, differing in their cause and age of onset (see Table 31-1). Severe adult hypothyroidism (myxedema) may occur idio-pathically or may be caused by specific factors such as autoimmune lymphocytic destruction (Hashimoto disease). In the child, thyroid function may be congenitally impaired, and cretinism will result if this condition is untreated. Hypothyroidism may result at any age if the dietary intake of iodine is extremely low. Several other forms of hypothyroidism that have a genetic or familial basis also exist.54... 

Hypothyroidism at birth is known as cretinism and is the most common preventable cause of mental retardation in the world. The incidence of cretinism is approximately... 

Fetal problems, including abortion, stillbirths, congenital anomalies, neurological cretinism. Goiter, hypothyroidism, impaired mental function, increased susceptibility to radiation. 

Hypothyrodism and hyperthyroidism can both be due to a number of causes, one of which is metabolic dysfunction. Hypothyroidism is caused by undersecretion, of thyroid hormones. In one form of childhood hypothyroidism, children born with abnormally small thyroids produce insufficient levels of the thyroid hormones T3 and T4, which are important for metabolically directed bone development. If detected in the first 6 months of life, this disorder can be treated with synthetic thyroid hormones such that its effects can be avoided. The most severe early onset hypothyroidisms are characterized by Cretinism, a type of dwarfism, and mental retardation. Adult hypothyroidism is called myxedema. Myxedema symptoms include slowed speech, yellowed skin, and generally slowed body functions. Myxedema can also be treated with synthetic T4, but if left untreated, can lead to coma. 

Liothyronine is used in the treatment of hypothyroidism, nontoxic goiter, cretinism, and myxedema. 

Thyroid extract is used in the treatment of hypothyroidism, myxedema, and cretinism. It is also used as a diagnostic agent and for suppression of pituitary thyroid-stimulating hormone. Synthetic derivatives are preferred because of uniform potency. 

Thyroid hormone stimulates production of IGF-I directly (liver) and indirectly (via increased growth hormone, GH). In adults with hypothyroidism, basal serum GH levels are normal, but the GH responses to provocative stimuli, nocturnal GH secretion, and serum IGF-I are all subnormal. In cretinism (infantile hypothyroidism), linear growth is severely retarded and the resultant dwarfism is characterized by a retention of the high upper to lower body ratio of infancy. The growth retardation in persons with cretinism is primarily due to delayed appearance of ossification centers in long bone, and secondarily to a deficiency in growth factors. 

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