Correct Option: A

Melanocyte-stimulating hormone (MSH) or Melanotropin is secreted by the intermediate lobe of adenohypophysis (pars intermedia) of pituitary gland in mammals (other than man) so named ‘intermedin’. In lower vertebrates, it targets chromatophores & does wider distribution of the melanin grannules in chromatophores, so that the skin colour darkens. In birds & human beings and other mammals its role is uncertain but in man it is probably responsible for bronzing of skin, moles etc.