**Cretinism** is not a hereditary disease.

**Explanation:**

Hereditary diseases are those that are passed down from parents to their offspring through genetic inheritance. These diseases are caused by abnormalities or mutations in the genes. In the given options, three out of the four diseases are hereditary, while one is not.

1) **Cretinism**: Cretinism is a condition caused by a congenital deficiency of thyroid hormones. It leads to stunted physical and mental growth, as well as other symptoms like intellectual disability, hearing loss, and delayed development. Cretinism can be classified into two types: congenital hypothyroidism and maternal hypothyroidism. Congenital hypothyroidism is caused by a defect in the thyroid gland, while maternal hypothyroidism occurs when the mother's thyroid hormones are insufficient during pregnancy. Cretinism is not a hereditary disease but rather a result of a deficiency in thyroid hormones, which can be caused by various factors such as iodine deficiency or maternal thyroid disorders.

2) **Cystic fibrosis**: Cystic fibrosis is a hereditary disease caused by a mutation in the CFTR gene. This gene is responsible for producing a protein that regulates the movement of salt and water in and out of cells. The mutation leads to the production of a defective CFTR protein, which results in the buildup of thick, sticky mucus in various organs, especially the lungs and digestive system. Cystic fibrosis is inherited in an autosomal recessive manner, meaning that both parents must carry a copy of the mutated gene for their child to be affected.

3) **Thalassaemia**: Thalassaemia refers to a group of inherited blood disorders characterized by abnormal hemoglobin production. Hemoglobin is the protein responsible for carrying oxygen in the red blood cells. Thalassaemia can be caused by mutations in the genes that control the production of alpha or beta globin chains. The severity of thalassaemia symptoms varies depending on the type and number of gene mutations inherited. Thalassaemia is also inherited in an autosomal recessive manner.

4) **Haemophilia**: Haemophilia is a hereditary bleeding disorder caused by a deficiency or abnormality in one of the blood clotting factors, specifically factor VIII (hemophilia A) or factor IX (hemophilia B). These clotting factors are essential for the normal formation of blood clots to prevent excessive bleeding. Hemophilia is inherited in an X-linked recessive manner, which means that the mutated gene responsible for the disorder is located on the X chromosome. As a result, hemophilia predominantly affects males, while females are typically carriers of the mutated gene.

In summary, cretinism is not a hereditary disease, while cystic fibrosis, thalassaemia, and hemophilia are all inherited in different patterns.

Answer is cretinism because it is caused due to deficiency of thyroid hormone