Michelangelo's caricature found hidden in his famous work

Italian artist Michelangelo inserted a caricature of himself into a sketch of his close friend Vittoria Colonna made in the 16th century, a study has found.

The artwork, currently in the collection of the British Museum in the UK, may serve as a tool for analysing the artist's probable bodily dimensions and even his state of health at the time.

"Michelangelo Buonarroti (1475-1564), like many other renowned artists of his time, included a self-portrait in many of his works," Deivis de Campos of the Federal University of Health Sciences in Brazil wrote in the study.

In the portrait of Colonna, a small figure can be seen standing in the area immediately in front of her abdomen and between the lines that form part of her dress.

The caricature is leaning forward at an acute angle, as if he himself were drawing the portrait.

The caricature may have been a signature of sorts, said de Campos lead author of the study published in the journal Clinical Anatomy.

During Michelangelo's time, there were many restrictions on artists and their work, perhaps the main one being that artists were not allowed to sign their works, said de Campos.