It is a section of tissue sometimes called a middle or intermediate lobe, between the pars distalis, and the posterior pituitary.

[4] In some animals including amphibians[5] it mediates active camouflage, causing darkening of the skin when placed against a darker background.

[5] The pars intermedia is responsible for secreting α-melanocyte-stimulating hormone, and corticotropin-like intermediate peptide.

The characteristic pattern of skin hyperpigmentation seen during pregnancy may be a result of increased circulating maternal a-MSH (which may have originated from either the maternal or fetal pars intermedia), but a-MSH secretion does not seem to be involved in skin tanning in response to light exposure.

[citation needed] This color change is due to MSH stimulating the dispersion of melanin pigment in the animal's skin melanocyte chromatophores.