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Cretinism: Congenital Hypothyroidism

Cretinism: Congenital Hypothyroidism

Cretinism, often known as congenital hypothyroidism, is a disorder in which infants produce thyroid hormones insufficiently. This hormone shortage can cause serious physical and cognitive difficulties if left untreated. Early detection and prompt management are essential to reduce the long-term effects and guarantee healthy development for affected newborns.

Table of Contents:

  • What is Cretinism?
  • Thyroid Hormone Synthesis and Secretion
  • Types of Cretinism
  • Causes
  • Diagnosis
  • Treatment
  • Practice Problems 
  • Frequently Asked Questions

What is Cretinism?

Cretinism is a rare but deadly illness that develops when a newborn's thyroid hormone production is insufficient. When thyroid hormones are inadequate during crucial growth phases, it can cause severe mental and physical deficits. Thyroid hormones are essential for the development of the brain and body. 

Cretinism can cause stunted growth, intellectual difficulties, delayed puberty, and other related health problems if it is not treated. However, the risk of long-term consequences can be reduced with early detection through newborn screening and rapid treatment, allowing those who are affected to have relatively normal lives.

Thyroid Hormone Synthesis and Secretion

Thyroid hormone synthesis occurs within the thyroid gland within the visceral compartment of the neck. The main ideas of thyroid hormone production and secretion are as follows:

  • Iodide is absorbed by thyroid follicular cells from the circulation.
  • Iodide is converted to iodine inside follicular cells.
  • Thyroglobulin, a large protein produced by the thyroid gland, has iodine integrated into tyrosine residues.
  • The active forms of thyroid hormone, thyroxine (T4) and triiodothyronine (T3) are created by coupling iodinated tyrosine residues.
  • The pituitary gland's thyroid-stimulating hormone (TSH) induces the release of T3 and T4 from the follicular cells.
  • In the bloodstream, T3 and T4 are released and bind to transport proteins.
  • The conversion of T4 into T3, which is the thyroid hormone's more active form, occurs in target tissues.
  • T3 controls the expression of genes and affects a variety of physiological processes by attaching to nuclear receptors in target tissues.
  • Thermoregulation, growth, development, and metabolism are all significantly influenced by thyroid hormones.

Types of Cretinism

There are two types of cretinism:

Congenital Cretinism

Cretinism which is a congenital hypothyroidism non-goitrous (CHNG), is called congenital cretinism. It occurs in a ratio of 1:3000 to 1:4000 in an iodine-deficient area and is considered the most occurring inborn endocrine disorder. A defect in the genes responsible for encoding various enzymes involved in synthesising thyroid hormone (thyroglobulin, iodotyrosine deiodinase and TSH) can cause this type of cretinism.

Endemic Cretinism

This occurs in children who live in iodine-deficient geographical settings. The woman who had been affected with maternal hypothyroidism bears children with endemic cretinism. This may occur due to using sulfonamides or antithyroid drugs during pregnancy.

  • Neurological cretinism – The conditions include deaf-mutism, retarded growth, motor spasticity, squint, and severe mental retardation.
  • Myxedematous cretinism– The conditions include incomplete maturation of facial expression, retarded growth, mental retardation, dry and thickened dry skin, dry and scarce hair, dry and small eyebrows and eyelashes, and delayed sexual maturation.

Causes

The primary cause of cretinism is usually attributed to iodine deficiency or impaired thyroid function. Here are some common causes and contributing factors:

  • Iodine deficiency- Lack of dietary iodine which affects the thyroid gland's ability.
  • Genetic factors- Mutations or abnormalities interfere with the development or function of the thyroid gland.
  • Maternal factors- Untreated or poorly controlled hypothyroidism in pregnancy.
  • Medications and radiation exposure- Antithyroid drugs or radioactive iodine during pregnancy.
  • Inherited enzyme defects- Disrupt the synthesis or metabolism of thyroid hormones.

Cretinism can be prevented by ensuring proper iodine supplementation, which is often incorporated into public health programs in many countries. Timely diagnosis and treatment play a critical role in preventing long-term complications and promoting the overall development and well-being of individuals affected by this condition.

Diagnosis

Diagnosis of cretinism involves several key points and assessments. Here are the main steps involved:

  • Clinical evaluation: It might include looking for characteristic signs and symptoms such as stunted growth, a protruding tongue, delayed development, a puffy face, dry skin, a broad nose, and other related physical abnormalities.
  • Medical history: Gather individuals’ such as family history of thyroid disorders, exposure to potential maternal risk factors, and any other related symptoms observed by caregivers.
  • Thyroid function tests: Blood tests such as T4 and thyroid-stimulating hormone (TSH) measurements.
  • Newborn screening: To detect congenital hypothyroidism after birth, such as a blood sample from the newborn's heel for TSH level testing.
  • Imaging studies: Ultrasound or scintigraphy to assess the thyroid gland's size, structure, and function.
  • Genetic testing: To identify any specific gene mutations or enzyme defects that could result in the condition.

Treatment

In order to address the underlying hypothyroidism, thyroid hormone replacement therapy is the foundation of cretinism treatment. Enlisted below are key points regarding the treatment options for cretinism:

Synthetic thyroid hormone: Levothyroxine (T4) is taken orally to replace the deficient thyroid hormone. 

  • Early initiation of treatment: Treatment promptly after diagnosis (especially in newborns) to prevent further developmental delays and promote normal growth. 
  • Regular monitoring: Growth parameters, thyroid hormone levels, and developmental milestones to ensure proper dosage adjustment and optimal management of cretinism.
  • Lifelong therapy: Thyroid hormone replacement therapy is necessary throughout life, with regular follow-up appointments to maintain stable hormone levels and monitor health.
  • Multidisciplinary approach: Comprehensive needs may include the involvement of paediatricians, endocrinologists, nutritionists, geneticists, and educational specialists.
  • Supportive interventions: Early intervention services, speech therapy, physical therapy, and educational support are required, along with replacement.

Practice Problems

Q1. Choose the primary cause of cretinism.

A. Iodine deficiency
B. Maternal diabetes
C. Genetic mutations
D. Exposure to radiation

Ans. A. Iodine deficiency

Iodine deficiency affects thyroid hormone production, so it is the primary cause of cretinism.

Q2. What is the diagnosis of cretinism in newborns?

A. Clinical evaluation
B. Genetic testing
C. Blood tests for TSH levels
D. Imaging studies

Ans. C. Blood tests for TSH levels

TSH levels, which can suggest hypothyroidism in blood testing on infants, are used to identify cretinism.

Q3. Which one is the primary treatment for cretinism?

A. Antibiotic therapy
B. Surgical intervention
C. Vitamin supplementation
D. Hormone replacement therapy

Ans. D. Hormone replacement therapy

Hormone replacement therapy, which handles the underlying thyroid hormone shortage, is the principal treatment for cretinism.

Frequently Asked Questions

Q1. What are cretinism and myxedema?
Answer : Myxedema is the term for severe hypothyroidism in adults and relates to swelling and thickening of the skin. Cretinism is a disorder of severe congenital hypothyroidism resulting in impaired physical and mental growth.

Q2. Why does hypothyroidism cause cretinism?
Answer :
Due to the potential for improper growth and development of the body and brain during crucial developmental stages, such as foetal development or early infancy, hypothyroidism can result in cretinism.

Q3. Which gland causes cretinism?
Answer :
The thyroid gland is the primary gland responsible for cretinism because it produces insufficient levels of thyroid hormones, which, if left untreated, can develop cretinism.

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