Circulating levels of insulin-like growth factor binding protein 3 (IGFBP-3) and insulin-like growth factor I (IGF-I) in perimenopausal women

Reference Ranges of Serum Insulin-Like Growth Factor-I and Insulin-Like Growth Factor Binding Protein-3: Results from a Multicenter Study in Healthy Korean Adults

Insulin-like growth factor-I (IGF-I) plays a pivotal role in the diagnosis and treatment of growth hormone (GH) excess or deficiency. The GH study group of the Korean Endocrine Society aims to establish the Korean reference ranges of serum IGF-I and insulin-like growth factor binding protein-3 (IGFBP-3) and assess the relationship between IGF-I and IGFBP-3 and clinical parameters. Fasting serum was collected from healthy Korean adults at health promotion centers of five hospitals nationwide. Serum IGF-I and IGFBP-3 were measured via an immunoradiometric assay using a DSL kit (Diagnostic Systems Laboratories). Serum samples from 354 subjects (180 male, 174 female) were analyzed based on sex at 10-year intervals from 21 to 70 years. IGF-I levels were inversely correlated with age. After adjustment of age, the IGF-I/IGFBP-3 ratio was significantly negatively associated with blood pressure and free thyroxine and positively associated with weight, hemoglobin, creatinine, alanine transferase, fasting glucose, and thyroid stimulating hormone. Therefore, age- and sex-specific reference ranges of serum IGF-I and IGFBP-3 can be efficient in evaluating GH excess or deficiency in Korean population.

The association between insulin-like growth factor 1 (IGF-1), IGF-binding proteins (IGFBPs), and the carboxyterminal propeptide of type I procollagen (PICP) in pre- and postmenopausal women with rheumatoid arthritis

OBJECTIVES

To assess the association between plasma levels of the insulin-like growth factor (IGF) system including IGF-1, IGF-binding proteins (IGFBPs) including IGFBP-1, total (t-)IGFBP-3 and functional (f-)IGFBP-3, and the carboxyterminal propeptide of type I procollagen (PICP) in pre- and postmenopausal women with rheumatoid arthritis (RA).

METHOD

Plasma concentrations of IGF-1, IGFBP-1, t-IGFBP-3, f-IGFBP-3, and PICP were measured by immunoassay.

RESULTS

No significant difference was observed in plasma IGF-1 levels between pre- and postmenopausal subjects. Plasma levels of IGFBP-1 were elevated in RA. PICP and f-IGFBP-3 were greatly affected by menopausal status. Of the three IGFBPs tested, only f-IGFBP-3 plasma levels in RA women correlated negatively with age and disease duration. A positive correlation was demonstrated between PICP and erythrocyte sedimentation rate (ESR) in RA. Moreover, there was no correlation between PICP and IGF-1 and any of the IGFBPs in RA women.

CONCLUSIONS

Considerable disruption of the IGF system in RA was found to be related to disease activity and duration. Changes in the IGF-IGFBP axis and PICP levels were different in pre- and postmenopausal women with RA. Elevated plasma PICP concentrations may indicate an increased rate of bone formation in postmenopausal RA women. Additionally, the observed changes in the IGF/IGFBP system did not affect bone formation during RA.

Effect of GH/IGF-1 on Bone Metabolism and Osteoporsosis

Background. Growth hormone (GH) and insulin-like growth factor (IGF-1) are fundamental in skeletal growth during puberty and bone health throughout life. GH increases tissue formation by acting directly and indirectly on target cells; IGF-1 is a critical mediator of bone growth. Clinical studies reporting the use of GH and IGF-1 in osteoporosis and fracture healing are outlined. Methods. A Pubmed search revealed 39 clinical studies reporting the effects of GH and IGF-1 administration on bone metabolism in osteopenic and osteoporotic human subjects and on bone healing in operated patients with normal GH secretion. Eighteen clinical studies considered the effect with GH treatment, fourteen studies reported the clinical effects with IGF-1 administration, and seven related to the GH/IGF-1 effect on bone healing. Results. Both GH and IGF-1 administration significantly increased bone resorption and bone formation in the most studies. GH/IGF-1 administration in patients with hip or tibial fractures resulted in increased bone healing, rapid clinical improvements. Some conflicting results were evidenced. Conclusions. GH and IGF-1 therapy has a significant anabolic effect. GH administration for the treatment of osteoporosis and bone fractures may greatly improve clinical outcome. GH interacts with sex steroids in the anabolic process. GH resistance process is considered.

The insulin-like growth factor-I system and hormone replacement therapy

OBJECTIVE

To determine the effects of hormone replacement therapy on plasma concentrations of free and total insulin-like growth factor (IGF)-I, IGF binding protein (BP)-1, and IGFBP-3.

DESIGN

Clinical study.

SETTING

Gynecologic clinic at a university hospital.

PATIENT(S)

Seventy-one postmenopausal women.

INTERVENTION(S)

Six cycles of four different hormonal replacement therapy regimens: oral conjugated estrogens, transdermal estradiol, oral conjugated estrogens and norethisterone, and transdermal estradiol and norethisterone acetate.

MAIN OUTCOME MEASURE(S)

Blood samples were collected before and after treatment for measurement of free and total IGF-I, IGFBP-1, and IGFBP-3.

RESULT(S)

Conjugated estrogen replacement therapy is associated with a decrease in plasma concentration of total IGF-I and increase in concentrations of free IGF-I and IGFBP-1. Transdermal estrogens have no effect on total and free IGF-I and IGFBP-1 concentrations. Oral norethisterone plus conjugated estrogens increased free IGF-I and IGFBP-1 concentrations but did not change IGF-I concentrations. Transdermal conjugated estrogens plus norethisterone acetate increased free IGF-I concentrations but not total IGF-I or IGFBP-1 concentrations. The plasma concentration of IGFBP-3 did not change in any group.

CONCLUSION(S)

Alterations in total IGF-I concentration can occur depending on the route of hormone replacement therapy administration. Free IGF-I concentrations were elevated in all study groups except that treated with transdermal estrogens.

A 3-year study of prevention of postmenopausal bone loss: conjugated equine estrogens plus medroxyprogesterone acetate versus tibolone

The aim of this study was to investigate the effects of tibolone in the prevention of postmenopausal bone loss over 3 years, and to compare these with the effects of sequential hormone replacement therapy. Forty early postmenopausal women were randomized to a 21-day regimen of conjugated equine estrogens (CEE, Premarin) plus sequential medroxyprogesterone acetate (MPA, Prodafem), or tibolone (Livial) daily. In total, 36 women completed 12 months and were considered for the intent-to-treat analysis, 34 completed 24 months and 23 completed 36 months. Main drop-out reasons were: lost to follow-up (n = 9) and minor side-effects (n = 4). Bone mineral density was measured at baseline and after 6, 12, 24 and 36 months, using dual-energy X-ray absorptiometry at the lumbar spine and the upper femur (neck, trochanter, total hip). In both groups, bone loss was prevented. Treatment with tibolone demonstrated significant increases in bone density at the spine (+4.6%; p < 0.01), at the total hip (+3.2%; p < 0.01) and at the trochanter (+4.5%; p < 0.01), whereas the CEE/MPA group showed a non-significant increase of bone mineral density at the lumbar spine (+2.6%) but no increases at the hip. Between-group differences in bone mineral density changes were significant (p < 0.05) for the total hip and the trochanter at 36 months. This increase of bone mineral density was not accompanied by changes in insulin-like growth factor-I (IGF-I) or insulin-like growth factor binding protein-3 (IGFBP-3) in either group. Osteocalcin, alkaline phosphatase and urinary ratios of hydroxyproline/creatinine and calcium/creatinine significantly decreased in both groups. In conclusion, sequential CEE/MPA prevented cortical and trabecular bone loss, with a transient increase of bone mineral density only during the first 6 months. Tibolone not only prevented cortical and trabecular bone loss, but further increased bone mineral density at the lumbar spine and at the hip throughout the 3 years of treatment, suggesting a sustained positive effect on bone mass.