Fig. 6.

Prolactin (PRL) and Covid-19 severity: SARS-CoV-2 induces activation of pro-inflammatory cytokines, toll-like receptor 4 (TLR4), and mitogen-activated protein kinase (MAPK), with inhibition of thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), and calcitonin gene-related peptide (CGRP) leading to activation of PRL release, which in turn stimulate inflammatory protein-1α (MIP-1α) and interferon protein 10 (IP-10) with inhibition of regulatory T cell (Treg), leading to hyperinflammation and Covid-19 severity