Sex hormone binding globulin

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Sex hormone binding globulin
Sex hormone binding globulin
Model with 5α- dihydrotestosterone (green) according to PDB  1D2S

Existing structural data: see UniProt

Properties of human protein
Mass / length primary structure 373 amino acids
Secondary to quaternary structure Homodimer
Isoforms 2
Identifier
Gene name SHBG
External IDs
Occurrence
Homology family SHBG
Parent taxon Euteleostomi

Sex hormone binding globulin (SHBG) is a specific transport protein for sex hormones , especially testosterone and estradiol . These hormones bind in blood of vertebrates to SHBG, and to a lesser extent to albumin . Only a small percentage is unbound. Only this unbound part can become active in the target organs, SHBG has an inhibiting influence on their effect and is libido- lowering.

SHBG is produced by liver cells and released into the bloodstream. It is also produced by the brain , uterus , placenta, and vagina . SHBG produced by the testes is also known as androgen-binding protein . The sequence of the amino acids is the same, it only differs in a few functional sugar groups. The gene for SHBG is on chromosome 17 .

The concentration of SHBG in the blood is controlled by various stimulating and inhibiting factors. Insulin and insulin-like growth factor seem to have a lowering effect, as do high concentrations of androgen , while high estrogen and thyroxine concentrations increase the effect. More recent studies, however, suggest that gene expression is inhibited by the fat production of the liver cells, which results in a reduction in the concentration in the blood.

The SHBG concentration is chronically low in polycystic ovarian syndrome , diabetes mellitus and hypothyroidism . Increased concentrations can be found during pregnancy , with hyperthyroidism and anorexia nervosa .

In the laboratory, the simultaneous determination of SHBG and testosterone or estradiol can provide information about the concentration of the free, biologically active sex hormone.

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  1. ↑ Too much sugar turns off gene that controls the effects of sex steroids , accessed January 12, 2008
  2. ↑ a b Labor Lexicon for SHBG

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