Question

Which of the following is not a hereditary disease?
A. Cretinism
B. Cystic fibrosis
C. Thalassemia
D. Haemophilia

Answer 1

Hint: Hereditary diseases are generally caused due to chromosomal disorders, whereas non-hereditary diseases can be caused by several factors like hormone deficiency, exposure to mutagens, lack of nutrition, etc.

Complete answer:
Cretinism is a non-hereditary disease that is caused in infants due to decrease triiodothyronine (T3) and tetraiodothyronine (T4) hormone synthesis and secretion. The infant is mentally retarded and is called a cretin. The main reason as to why cretinism is seen in children is iodine deficiency. Iodine is required for the synthesis of both T3 and T4 hormones.

Additional Information: The hormones T3 and T4 both are secreted by the thyroid gland and fluctuation in the amount secreted can cause the following disorder:

Deficiency Disorders or Hypothyroidism:
-Cretinism: Seen in infants, symptoms include low IQ, abnormal skin, deaf-mutism. Low heart rates are observed.
-Myxoedema or Gull's disease: Seen in adults, deposition of myxomatous (mucopolysaccharides tissue) tissue is seen, which results in the puffy appearance of face and neck, lowered heart rate, decreased blood pressure.
-Simple or Endemic Goitre: It happens due to iodine deficiency, and iodine is required for thyroid hormone synthesis. Lower concentration of thyroid is blood results in increased secretion of TSH due to feedback mechanisms. Due to the oversecretion of TSH, swelling of the thyroid gland occurs.

Hyperthyroidism:
-Grave’s Disease: Happens due to over secretion of thyroid hormones, protruding eyeballs, or exophthalmos is seen. The main symptom is an exophthalmic goiter. Insomnia and anxiety are also found in people suffering from Grave’s disease.
-Plummer’s Disease: Toxic nodulations appear inside the thyroid gland tissue.

So, the correct answer is,” Cretinism is not a hereditary disease out of the following.”

Note: It is important to know that even though both T3 and T4 are thyroid hormones, T3 is almost four times more biologically active than T4. As both T3 and T4 require iodine for their synthesis, therefore when deficiency of iodine occurs, low production of these hormones results in cretinism.