sex hormone-binding globulin; SHBG; Sex steroid-binding protein; SBP; testis-specific androgen-binding protein; ABP; testosterone-estrogen-binding globulin; testosterone-estradiol-binding globulin; TeBG (SHBG)

Function

• androgen transport protein, but may also be involved in receptor mediated processes
• functions as a homodimer
• each dimer binds one molecule of steroid
• specific for 5-alpha-dihydrotestosterone, testosterone, & 17-beta-estradiol
• regulates plasma metabolic clearance rate of steroid hormones by controlling their plasma concentration
• testosterone is transported in circulation bound to SHBG*.
• only 1-3% of testosterone is free (active form)

* non-specific binding of testosterone to albumin occurs

Structure

contains 2 laminin G-like domains

Compartment

• secreted (putative)
• in testis, it is synthesized by the Sertoli cells, secreted into the lumen of the seminiferous tubule & transported to the epididymis

Alternative splicing

• named isoforms=2;
• additional isoforms seem to exist

Expression

• isoforms 1 & 2 are present in liver & testis
• in testis, it is synthesized by the Sertoli cells
• expression may be inhibited by insulin & prolactin

Pathology

• increased serum SHBG levels
  • hyperthyroidism
  • hyperestrogenic states
    • pregnancy
    • oral contraceptives
    • gynecomastia
• decreased serum SHBG
  • insulin resistance
  • increased risk of type-2 diabetes

More general terms

• globulin
• plasma protein
• glycoprotein

Additional terms

• sex hormone-binding globulin (SHBG) in serum

Database

• UniProt: http://www.uniprot.org/uniprot/P04278.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=6462
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:6462
• OMIM: https://mirror.omim.org/entry/182205