Which of these diseases is not related to thyroid glands?

The correct option is Acromegaly.

To understand why this is the correct answer, let us analyze each of the diseases mentioned in the options and their relationship with the thyroid gland:
1. Cretinism: This is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones (hypothyroidism) during early childhood.
2. Myxoedema: This term refers to severe hypothyroidism (underactive thyroid gland) in adults, characterized by swelling of the skin and underlying tissues, giving a waxy consistency, along with weight gain and mental dullness.
3. Goitre: This is an abnormal enlargement of the thyroid gland, which commonly develops as a result of iodine deficiency or inflammation of the thyroid gland (associated with hypothyroidism or hyperthyroidism).
4. Acromegaly: This is a hormonal disorder that develops when the pituitary gland (not the thyroid gland) produces too much growth hormone (GH) during adulthood, leading to the abnormal enlargement of bones in the hands, feet, and face.

Therefore, among the given options, Acromegaly is the only disease that is not related to the thyroid gland.