Effect of corticoid therapy on growth hormone secretion

The limited screening value of insulin-like growth factor-I as a marker for alterations in body composition in very long-term adult survivors of childhood cancer

BACKGROUND

The clinical relevance of low IGF-I levels, caused by cranial radiotherapy, in adult childhood cancer survivors has not been studied extensively. We evaluated whether IGF-I is a useful marker for altered body composition and growth hormone deficiency (GHD) in this group.

PROCEDURE

We analyzed retrospective data from 610 adult childhood cancer survivors, retrieved from the late effects clinic. Median age at diagnosis was 6 years (interquartile range 3-11) and follow-up time was 18 years (13-24). We assessed IGF-I standard deviation scores (SDS), anthropometrical measures, growth hormone stimulation tests in patients with clinical signs of GHD, and measures of body composition (assessed by dual X-ray absorptiometry, Lunar Prodigy).

RESULTS

In 58 cranially irradiated acute leukemia survivors (25 Gy (24-25)) and 56 locally irradiated brain tumor survivors (42 Gy (35-54)) we found significantly lower IGF-I SDS (P < 0.001), lower height SDS (P < 0.001), higher body mass index (P = 0.01), higher waist-hip ratio (WHR; P = 0.001), higher total fat percentage SDS (P < 0.001), and lower lean body mass SDS (P < 0.001), as compared to 452 not cranially irradiated survivors. IGF-I showed a weak inverse correlation with BMI (r = -0.12, P = 0.04), WHR (r = -0.15, P = 0.01), total fat percentage (r = - 0.14, P = 0.02), and a positive correlation with lean body mass (r = 0.15, P = 0.01). In patients with low IGF-I levels, IGF-I did not significantly differ between subjects with and without GHD as determined by GH-stimulation testing (P = 0.39).

CONCLUSION

This study shows that IGF-I has limited value as a marker for alterations in body composition in adult childhood cancer survivors.

Growth hormone cannot enhance the recovery of dexamethasone-induced osteopenia after withdrawal in young female wistar rats

Dexamethasone (DEX) suppresses the secretion of and responsiveness to growth hormone (GH). Here we aimed to assess the therapeutic effects of GH on the DEX-induced osteopenia. Female Wistar rats were treated for 2 weeks with DEX (200 microg/day) or saline as a control. DEX significantly decreased body weight gain, bone mineral density (BMD), growth plate thickness, area ratio of trabecular bone, and serum osteocalcin levels. DEX also elongated the tibia primary spongiosa and caused many tiny lipid droplets in the tibia marrow. These results indicated that DEX induced osteopenia in rats. We then assessed the effects of GH on the recovery of osteopenia after withdrawal of DEX. DEX-treated rats were subsequently treated for 1 week with GH (0.1 or 0.3 U/day) or saline, while saline-pretreated rats were treated for 1 week with saline as a control. GH (0.1 or 0.3 U/day)-treated rats showed a catch-up growth in various bone measurements by one week after DEX withdrawal, though most of them remained subnormal. GH treatment did not enhance the recovery of DEX-induced osteopenia. Therefore a short-term exposure to DEX significantly impaired the bone metabolism, which started to recover soon after withdrawal of DEX. Unfortunately, immediate administration of GH after withdrawal of DEX did not enhance the recovery process.

Direct effects of corticotrophin-releasing hormone on stimulated growth hormone secretion

OBJECTIVE

This study evaluated the effect of corticotrophin-releasing hormone (CRH) on growth hormone releasing hormone (GHRH)-stimulated growth hormone (GH) release in man.

DESIGN

Six healthy adult volunteers (age 20-35 years) were studied. On different occasions they each received an intravenous bolus of saline, CRH(1-41) (100 micrograms), adrenocorticotrophic hormone (ACTH) [Synacthen (500 ng/m2)] or hydrocortisone (50 mg), followed 30 minutes later by an intravenous bolus of either GHRH-(1-29)-NH2 (1.0 microgram/kg) or saline.

MEASUREMENT

Serum GH concentrations were measured using an immunoradiometric assay, and cortisol concentrations were measured by commercial radioimmunoassay. TSH concentrations were measured using a solid phase immunoradiometric assay kit.

RESULTS

Pretreatment with CRH(1-41) attenuated the GH response to GHRH [saline/GHRH-(1-29)-NH2 20.2 +/- 6.2 mU/l; CRH(1-41)/GHRH-(1-29)-NH2 10.9 +/- 2.8 mU/l (P = 0.01)]. This effect was not due to the rise in ACTH or cortisol induced by CRH(1-41), since pretreatment with either ACTH or hydrocortisone significantly augmented the GH response to GHRH-(1-29)-NH2 in the same subjects [ACTH/GHRH-(1-29)-NH2 30.3 +/- 8.8 mU/l (P = 0.01); hydrocortisone/GHRH-(1-29)-NH2 36.4 +/- 11.2 mU/l (P = 0.02)].

CONCLUSION

Our data suggest that the inhibitory effect of CRH(1-41) on GHRH-(1-29)-NH2-induced GH release is not a result of ACTH or cortisol release but reflects a direct action of CRH on GH secretion, possibly via stimulation of somatostatin release. The acute rise in GH following glucocorticoid administration could be explained in part by a rapid suppression of endogenous CRH.

Influence of treatment modalities on body weight in acute lymphoblastic leukemia

Weight for height of 92 patients (51 girls and 41 boys) treated for acute lymphoblastic leukemia (ALL) was evaluated in a longitudinal study. Fifty-four patients received cranial irradiation (CI) with a dose of 18 or 24 Gy and 38 patients did not receive CI. Seventy-seven patients were treated according to a normal-risk protocol and 15 patients received more intensive chemotherapy according to a high-risk protocol. In most of the patients the duration of follow-up was 12 years for irradiated patients and 4.5 years for the nonirradiated patients. Thirty of 92 patients were treated according to a protocol without CI, but with a difference in the use of corticosteroids: 19 patients received dexamethasone during the remission-induction and maintenance treatment and 11 patients received prednisone. The influence of dexamethasone vs. prednisone, sex, CI and high-dose vs. low-dose chemotherapy on weight for height was evaluated. Patients who received dexamethasone showed a significant increase in weight for height immediately after the start of therapy. In patients who received CI, weight for height significantly increased after the first year of treatment. The overweight in these patients persisted during the whole follow-up period. The weight for height of patients treated with prednisone and of patients who did not receive CI was below the mean of the normal population during treatment but was not different from normal after cessation of therapy. No difference in weight gain was seen between boys and girls and between patients who were treated with high vs. normal-risk protocols.

Growth hormone responses to growth hormone-releasing hormone and clonidine in dogs with Cushing's syndrome

The effects of clonidine, a growth hormone (GH) secretagogue, acting at the hypothalamic level and synthetic GH-releasing hormone (GHRH), a physiological stimulus of somatotrophs, on GH secretion were measured in 11 dogs with Cushing's syndrome. Eight healthy dogs served as controls. After the administration of GHRH the dogs with hyperadrenocorticism had a mean (SEM) GH peak of 11.2 (2.5) ng ml-1 which was significantly lower than the peak of 48.6 (13.4) ng ml-1 observed in the healthy dogs. Similarly, the GH response to clonidine was inhibited in the dogs with hyperadrenocorticism, the mean GH peak being 9.3 (3.3) ng ml-1 compared with 135.6 (43.3) ng ml-1 in the control dogs. No significant difference between the GH responses to GHRH and clonidine was observed in the dogs with Cushing's syndrome, the areas under the response curves being 567.9 (78.2) and 478.0 (102.6) ng.min ml-1, respectively. These results demonstrate that the function of somatotrophs is abnormal in dogs with Cushing's syndrome. There is evidence that the likely action of clonidine in dogs is to inhibit the release of somatostatin and the results therefore suggest that the effect of an excess of glucocorticoid in the dog is probably not mediated through an increase in somatostatin tone.