Inhibition of sex hormone-binding globulin production in the human hepatoma (Hep G2) cell line by insulin and prolactin.
Level 5 - mechanism / opinion, no new human data
In vitro bench study using a human cell line without clinical human data
PubMed 2842359 · doi:10.1210/jcem-67-3-460
What was done
Hep G2 human hepatoma cells were grown to near confluence and subsequently incubated for 72 hours in serum-free medium. Investigators measured sex hormone-binding globulin (SHBG) production and cell numbers following exposure to insulin (10⁻⁸ mol/L) and prolactin (10⁻⁸ mol/L), tested alone or in combination with estradiol (E2), thyroxine (T4), and testosterone (T).
What was found
Compared to control incubations (65.0 ± 0.6 nmol/10⁶ cells), both insulin (10⁻⁸ mol/L) and prolactin (10⁻⁸ mol/L) significantly decreased SHBG production to 46.8 ± 1.1 and 46.8 ± 1.2 nmol/10⁶ cells, respectively (P < 0.01). Insulin also suppressed E2- and T4-stimulated SHBG synthesis. Testosterone stimulated SHBG production to the same extent as estradiol. Both E2 and insulin significantly increased cell proliferation.
Why it matters
These findings identify direct hepatic inhibitory pathways for insulin and prolactin on SHBG production, providing a cellular mechanism for the low serum SHBG levels observed in hyperinsulinemic and hyperprolactinemic clinical states.
Limits
This study was conducted entirely in an immortalized human hepatoma cell line (Hep G2) in vitro, which may not fully reflect normal human liver physiology or in vivo pharmacokinetic dynamics. Specific replication counts and dose-response data were not reported in the abstract.
Cited by
- supports A lack of insulin signaling reduces the physiological capacity to suppress sex hormone binding globulin (SHBG).