pituitary gland morphology trait pituitary gland size trait Trait.ontology VT:0005361 Any measurable or observable characteristic related to the physical magnitude of the pituitary gland, the compound gland suspended from the base of the hypothalamus, which secretes somatotropins, prolactin, TSH (thyroid-stimulating hormone), gonadotropins, adrenal corticotropin, and other related peptides. diencephalon size trait