The function of SMIM20 (small integral membrane protein 20, Ensembl gene identifier ENSG00000250317) is as follows. [Small integral membrane protein 20]: Component of the MITRAC (mitochondrial translation regulation assembly intermediate of cytochrome c oxidase complex) complex, that regulates cytochrome c oxidase assembly (PubMed:26321642). Promotes the progression of complex assembly after the association of MT-CO1/COX1 with COX4I1 and COX6C (PubMed:26321642). Chaperone-like assembly factor required to stabilize newly synthesized MT-CO1/COX1 and to prevent its premature turnover (PubMed:26321642). . [Phoenixin-14]: Peptide involved in a broad spectrum of regulatory functions (By similarity). Is a ligand for GPR173 (By similarity). As part of the reproductive cycle, it regulates gonadotropin-releasing hormone (GnRH) signaling in the hypothalamus and pituitary gland which augments the release of luteinizing hormone (By similarity). Plays a protective role in memory retention through activation of GNRHR (By similarity). Regulates the secretion of AVP by hypothalamic neurons (By similarity). Plays a role in the transduction of the itch sensation (By similarity). Induces anxiolytic effects, reducing behavior associated with anxiety (By similarity). Regulates food intake as well as satiation and satiety (By similarity). In the ovary, it regulates follicular growth by stimulating granulosa cell proliferation by increasing the expression of GPR173, CREB1, CYP19A1, KITLG, FSHR, and LHCGR (PubMed:30933929). It also increases the production of estradiol (E2) (PubMed:30933929). In the heart, it regulates contractility and relaxation (By similarity). It also plays a cardioprotective role during ischemia, where it activates the SAFE and RISK pathways (By similarity). Stimulates the proliferation and differentiation of preadipocytes (By similarity). In pancreatic islet cells, it induces proliferation of islet cells as well as the production of INS (By similarity). {ECO:0000250|UniProtKB:C0HLM6, ECO:0000250|UniProtKB:D3Z7Q2, ECO:0000269|PubMed:30933929}. [Phoenixin-20]: Peptide involved in a broad spectrum of regulatory functions (By similarity). Is a ligand for GPR173 (By similarity). As part of the reproductive cycle, it regulates gonadotropin-releasing hormone (GnRH) signaling in the hypothalamus and pituitary gland which augments the release of luteinizing hormone (By similarity). Plays a protective role in memory retention through activation of GNRHR (By similarity). Regulates the secretion of AVP by hypothalamic neurons (By similarity). Plays a role in the transduction of the itch sensation (By similarity). Induces anxiolytic effects, reducing behavior associated with anxiety (By similarity). Regulates food intake as well as satiation and satiety (By similarity). In the ovary, it regulates follicular growth by stimulating granulosa cell proliferation by increasing the expression of GPR173, CREB1, CYP19A1, KITLG, FSHR, and LHCGR (PubMed:30933929). It also increases the production of estradiol (E2) (PubMed:30933929). In the heart, it regulates contractility and relaxation (By similarity). It also plays a cardioprotective role during ischemia, where it activates the SAFE and RISK pathways (By similarity). Stimulates the proliferation and differentiation of preadipocytes (By similarity). In pancreatic islet cells, it induces proliferation of islet cells as well as the production of INS (By similarity). {ECO:0000250|UniProtKB:C0HLM6, ECO:0000250|UniProtKB:D3Z7Q2, ECO:0000269|PubMed:30933929}.