Cretinism overview

# Overview
Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones (hypothyroidism). The term cretin refers to a person so affected. Cretinism is an old name used for congenital hypothyroidism. It includes sporadic cretinism and endemic cretinism. Sporadic cretinism is caused by gene mutations, radiation, drugs and so on. Usual symptoms are neurological impairment, low metabolism conditions and infertility. Thyroid hormone replacement is the main treatment. Endemic cretinism results from a diet deficient in iodine. Iodine deficiency results in enlargement of the thyroid gland, physical development, hypo-evolution and mental development impairment. As a public health problem, many countries have established the policy of iodine administration.

# Historical Perspective
Cretinism was first described by ancient Roman writers. Cretinism was described by physicians and travelers in the 19th century and some areas in Europe and North America were named as "goiter belts".

# Classification
Cretinism may be classified into two groups which are transient and permanent cretinism. Permanent cretinism can be more classified into primary and secondary subtypes.

# Pathophysiology
Cretinism is believed to be the result of a congenital anomaly in the thyroid gland. Cretinism can be caused by thyroid dysgenesis which is the most common cause of cretinism. Thyroid dysgenesis may be due to the absence of the thyroid gland, ectopic growth of the gland, or hypoplastic gland. Thyroid dysgenesis can be also due to mutations in genes as the TSH receptor gene, PAX8 gene, and NK2 homeobox 1. It is thought also that cretinism may be due to thyroid dyshormonogenesis. The decrease of thyroid hormone synthesis and secretion is due to impairment of thyroid peroxidase enzyme. Cretinism may be associated with some congenital anomalies like horseshoe kidney, ureterocele, hydrocele, and undescended testes.

# Causes
Cretinism may be caused by congenital causes like thyroid dysgenesis and ectopic thyroid. Cretinism can be caused by other causes like anti-thyroid medications and iodine deficiency.

# Differentiating Cretinism from other Diseases
Cretinism must be differentiated from other diseases that cause a failure to pass meconium or abdominal distension in infants, including meconium plug syndrome, small left colon syndrome, and Hirschsprung's disease.

# Epidemiology and Demographics
The incidence of cretinism is estimated to be 31.5 per 100,000 individuals in the United States. Cretinism is more in the Asian and Hispanic races more than the White and Black races. Cretinism affects the females more than males.

# Risk Factors
Common risk factors in the development of cretinism include post-dating delivery, macrosomia, mothers with anemia or goiter, and smoking parents. Other risk factors include cesarean section delivery and jaundice at the birth.

# Screening
According to  the Endocrine Society and the European Society for Pediatric Endocrinology, screening for cretinism is recommended in all neonates. Screening is important as early detection of cretinism will help in preventing the disease consequences as the mental retardation.

# Natural History, Complications and Prognosis
If left untreated, patients with cretinism may progress to develop mental retardation and neurological manifestations. Common complications of cretinism include growth retardation and cardiovascular problems. Prognosis is usually good with treatment with levothyroxine.

# Diagnosis

## History and Symptoms
The majority of patients with cretinism are asymptomatic. A positive history of a family member had the disease before and maternal history of thyroid problems is suggestive of cretinism. The most common symptoms of cretinism include lethargy, hoarse cry, constipation, and umbilical hernia. Less common symptoms of cretinism include palpable goiter.

## Physical Examination
Patients with cretinism usually appear asymptomatic at the beginning of the disease. Physical examination of patients with cretinism is usually remarkable for jaundice, dry skin, large fontanelles, macroglossia, umbilical hernia, bradycardia, delayed puberty, and hypotonia.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of cretinism include abnormal levels of thyroid hormones and thyroid stimulating hormone. High TSH and low T4 levels are consistent with primary cretinism. High TSH and normal T4 levels are consistent with sub-clinical cretinism.

## Electrocardiogram
There are no ECG findings associated with cretinism.

## X Ray
There are no x-ray findings associated with cretinism. However, knee x-ray may be helpful in evaluating the severity of cretinism. Knee x ray may show wide sagittal suture which indicates delayed bone maturation.

## CT
There are no CT scan findings associated with cretinism.

## MRI
There are no MRI findings associated with cretinism.

## Echocardiography or Ultrasound
The thyroid gland ultrasonography may be helpful in the diagnosis of cretinism. Findings on an ultrasound suggestive of cretinism include a thyroid gland in an ectopic location or a large gland which is suggestive of thyroid dyshormonogenesis.

## Other Imaging Findings
Thyroid radionuclide uptake and scanning may be helpful in the diagnosis of cretinism. The absence of the radionuclide uptake is consistent with somethyroid gland anomalies like ectopic thyroid gland, thyroid gland hypoplasia, and thyroid aplasia.

## Other Diagnostic Studies
There are no additional diagnostic studies for cretinism.

# Treatment

## Surgery
Surgical intervention is not recommended for the management of cretinism.

## Medical Therapy
The mainstay of treatment for cretinism is thyroid hormone replacement therapy. Levothyroxine (L-T4) is administrated orally to patients with cretinism.

## Primary Prevention
Effective measures for the primary prevention of cretinism include iodide supply in the diet and screening of the newborns.

## Secondary Prevention
There are no established measures for the secondary prevention of cretinism.

# Case Studies

## Case #1