Milena Orosco de Agudelo holds his 11-month-old son in her arm. The Colombian baby is already the weight of an average eight-year-old boy.[Agencies]

Doctors in Colombia are trying to determine how an 11-month-old baby is already the weight of an average eight-year-old.

The child's mother, Milena Orosco de Agudelo, said her son's unusual growth spurt began when he was just two months old.

He has had several medical examinations carried out which suggest he may have a problem with his endocrine system.

Miss Orosco de Agudelo said: "He had some tests done and the results show that he has a thyroid malfunction.

"Then, he had a cardiogram test done and that test shows that he has the bones of an eight-year-old boy, but they have not told me where that came from."

Doctor David Dias, of the Barranquilla Pediatric Hospital, said more examinations need to be carried out to discover why the child has become so large.

He said: "The baby will have tests done to see if he's obese or we're dealing with hyperthyroidism."

Hypothyroidism is often a result of an autoimmune condition known as Hashimoto's thyroiditis, in which the body's own immune cells attack and destroy the thyroid gland. Symptoms include fatigue and weight gain.

The normal weight for an 11-month-old boy is around one stone.

Because of his size, the boy's mother says he cannot fit into his older brother's hand-me-down clothes and is limited to wearing extra large nappies.