Secreted cytokine-like protein. Inhibits cell growth in vitro. Homodimer; disulfide-linked. Highly expressed in lung, where it localizes to epithelial cells lining the trachea and bronchi (PubMed:12406855, PubMed:12175512). Expression in lung is mainly restricted to bronchi, submucosal glands of the trachea, and tracheal epithelium, with little expression in terminal bronchioles (PubMed:12406855). Expressed in uterus where it localizes to epithelial cells of the uterine glands (PubMed:12175512). Also detected in heart, stomach and small intestine (PubMed:12175512). Detected in lung at embryonic stage 18.5 dpc. During gestation, expressed in the mammary gland from 6.5 dpc with highest expression at 10.5 dpc. Expression then declines, but later increases again during mammary gland involution at 4-21 days post partum. Belongs to the secretoglobin family. UGRP subfamily.