May regulate the number of excitatory synapses that are formed on hippocampus neurons. Has no effect on inhibitory synapses. May inhibit adipocyte differentiation at an early stage of the process. Forms homooligomers, predominantly dimers or trimers. Forms heterooligomers with C1QL1, C1QL2 and C1QL3, when proteins are coexpressed; this interaction does not occur after secretion (PubMed:23449976). Interacts with ADGRB3 (PubMed:21262840). Highly expressed in testis and adipose tissue, brown adipose tissue expressing higher levels than subcutaneous and visceral white adipose tissue. In gonadal fat pad, expressed at lower levels in adipocytes than in the stromal vascular fraction (VSP), which contains preadipocytes, fibroblasts, endothelial cells and occasional immune cells. Expression exhibits sexually dimorphism, with higher levels in females than in males. Down-regulated in fasted animals.