Effects Of Bovine Growth Hormone Research Articles

Effects of bovine growth hormone in suckling lambs.

The objective of this study was to determine the effects of bovine growth hormone (bGH) on body growth of suckling lambs. Suckling Merino lambs (fed on milk replacer from 4th day of life) were daily injected from 10th to 38th day of life with 80 micrograms bGH/kg b.w. Only insignificant increase of body weight was observed after 4 weeks of GH treatment. After 31st day of life body weight gain in the experimental lambs was significantly higher. It can be concluded that bGH increases body weight gain of lambs in 2nd month of life. It is probable that growth rate of sucklings is limited only by biological and biochemical capabilities of the organism and it can be hardly influenced by exogenous hormonal manipulation.

Effects of Bovine Growth Hormone in Infant Rats from Reduced Litters

The objective of this study was to determine the effects of growth hormone on body growth and the content of RNA, DNA and protein in liver, brain and heart muscle in rat pups from reduced nests. Suckling rats raised in litters of 4 youngs were daily injected from 3rd to 28th day of life with 1 microgram of bGH/g body weight. Our results show that GH administration evoked higher body weight gain and increase of tail length after 23rd day of life. There was significant increase of liver content of nucleic acids and protein. This GH-responsivity of pups from reduced nests might be related to differences in their metabolic profile and accelerated somatic and psychosocial development in comparison to normal youngs.

Effects of GH gene polymorphism and sex on carcass traits and fatty acid compositions in Japanese Black cattle

To investigate the effects of bovine growth hormone (bGH) gene polymorphism on carcass traits and fatty acid compositions in Japanese Black cattle caused by nucleotide substitution of CTG (allele A)/GTG (allele B) at codon 127 and of ACG (allele A and B)/ATG (allele C) at codon 172 of bGH, GH genotypes of 135 cattle were determined using allele specific-multiplex polymerase chain reaction (PCR). Allele A gave greater rib thickness and lower melting point of fat (MP) while allele B gave higher C18:1% (P < 0.05). Allele C gave higher C18:1, monounsaturated fatty acid (MUFA), unsaturated fatty acid (USFA) percentages (P < 0.05). It also gave lower saturated fatty acid (SFA) percentages, higher MUFA/SFA and USFA/SFA ratios, and lower MP (P < 0.05). Interactions of sex and GH alleles were analyzed. In heifers, allele A gave higher carcass weight, daily carcass gain, rib eye area, rib thickness, subcutaneous fat thickness, and BMS while allele B gave greater rib eye area and rib thickness (P < 0.05). Allele C gave higher C18:1 (P < 0.01), MUFA (P < 0.01), USFA percentages (P < 0.05) and MUFA/SFA and USFA/SFA ratios (P < 0.01), and lower C16:0 and SFA percentages (P < 0.05) and MP (P < 0.01). GH gene polymorphism affected carcass traits and fatty acid compositions although the effects were more pronounced in heifers.

Effects of bovine growth hormone (Posilac®) on growth performance, body composition, and IGFBPs in two strains of channel catfish

The effects of recombinant bovine growth hormone (rbGH; Posilac®) on growth rate, feed efficiency, body composition, and insulin-like growth factor binding proteins (IGFBPs) were investigated in Norris and NWAC103 strains of channel catfish. Three hundred and twenty fish from each strain were assigned randomly to four treatments with four replicates each. The treatments were (1) Sham-injected control (needle puncture per 3 weeks); (2) Low (30 μg g −1 BW per 3 weeks, Posilac®); (3) Medium (60 μg g −1 BW per 3 weeks, Posilac®); and (4) High (120 μg g −1 BW per 3 weeks, Posilac®). Fish were reared in 76-l tanks supplied with 26.0 °C flow-through well water for 9 weeks. Fish were fed a 36% CP commercial diet twice each day to apparent satiation. Feed consumption increased ( P<0.05) 15% with rbGH treatment in the Norris strain while no significant increase in feed consumption was observed in rbGH-treated NWAC103 catfish. Compared to sham controls, all treatments (Low, Medium, and High) increased final weights ( P<0.05) (168±13.2 vs. 144±10.0 g) (average weight of the three treatments), but no overall improvement in feed conversion ratio (FCR) was observed in NWAC103 fish. In the Norris strain, the High treatment increased ( P<0.05) final weight (135±6.2 vs. 106±8.7 g) but no improvement in FCR was observed when compared to sham controls. rbGH treatments increased ( P<0.05) total length in both strains, but no difference in condition factor (CF), hepatosomatic index (HSI), or body composition was observed. On day 63, levels of a 45-kDa IGFBP (catfish-IGFBP-3) were similar between treated and untreated fish in both strains. Results of this study indicate the Low treatment was as effective in promoting growth as the High treatment in the NWAC103 strain. Results of the body composition analysis suggest that the increase in weight gain was not due to an increase in fat deposition. The observed increase in length suggests rbGH enhances linear growth in channel catfish. Similar levels of cf-IGFBP-3 between treated and untreated fish may reflect “steady state” levels of cf-IGFBP-3 in growing fish. Identifying other endogenous growth factor(s) responsible for the observed increase in growth rate will be crucial in our understanding of improving growth in cultured channel catfish.

Stimulated growth hormone (GH) release in Friesian cattle with respect to GH genotypes.

The effects of bovine growth hormone (GH) polymorphism at the amino acid position 127 (substitution of leucine to valine) on milk and meat production traits have been reported; however, the physiological background of this influence has not yet been recognised. The aims of this study were to estimate allele frequencies of the growth hormone gene in a population sample of Friesian cattle, and to characterise the TRH-induced GH release with respect to GH genotypes. The analysis covered data on 214 Polish Friesians, aged 11 months, used to identify GH genotypes by the PCR-RFLP technique. Frequencies of leucine (Leu) and valine (Val) alleles were 0.69 and 0.31, respectively. The GH release was analysed after thyrotropin releasing hormone (TRH) stimulation in blood samples collected over a period of 2.5 h. There was a lack of significant difference in the overall characteristics of GH release in the blood of Friesian cattle with different GH genotypes (P > 0.05). Nevertheless, the Val/Val homozygotes had higher GH baselines both within heifers and bulls (14.1 +/- 2.8 and 14.6 +/- 2.0 ng.mL-1, respectively) than others. Moreover, males of the Val/Val genotypes showed the highest peak amplitude of GH release (55.5 +/- 8.1 ng.mL-1) in comparison to all other animals. The results presented provide evidence for the lack of difference in stimulated GH release with respect to GH genotypes in dairy cattle.

Effects of Bovine Growth Hormone (bGH) Transgene Expression or bGH Treatment on Reproductive Functions in Female Mice1

Both physiological and excessive levels of growth hormone (GH) can affect reproductive functions. Overexpression of human (h) or bovine (b) GH in transgenic female mice was previously reported to be associated with reproductive deficits. The objectives of the present study were to determine the age of onset of puberty, the length of the estrous cycle, and the ovulation rate in transgenic and normal mice from a line expressing bGH with the phosphoenolpyruvate carboxykinase (PEPCK) promoter and characterized by very high levels of transgene expression. Transgenic females reached puberty, defined as the appearance of the vaginal introitus, earlier than their normal littermates, but at a higher body weight. Compared to normal animals, an increased number of transgenic females failed to mate during the 15-day period of observation, and pregnancy rates were reduced. However, ovulation rates, as estimated by counting CL and implantation sites on Day 7 postcoitum, were increased in transgenic females. Plasma bGH levels in transgenic females ranged from 700 to 2200 ng/ml and were negatively correlated with fertility. To assess the effect of bGH on the ovulation rate in non-transgenic mice, normal females were paired with normal males and injected for up to 3 days with either 0.75 mg bGH/day or 0.30 mg bGH/day (injected as a single dose or as 0.15 mg twice daily). Data from animals that mated after at least 2 days of bGH treatment were analyzed. The ovulation rate was increased in females treated with 0.75 mg bGH/day, as compared to controls, and in females injected with 0.15 mg bGH twice daily as compared to those given 0.3 mg bGH/day and to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of Growth Hormone and Prolactin in the Induction of Vitellogenin Synthesis in Primary Hepatocyte Culture in the Eel, Anguilla japonica

Multihormonal effects of bovine growth hormone (GH) and ovine prolactin (PRL) on vitellogenin (Vg) synthesis in response to estradiol-17β (E 2) were electrophoretically examined in primary hepatocyte culture in the eel, Anguilla japonica. Newly synthesized protein after hormonal treatment was identified as Vg by immunoblot and immunoelectrophoresis. A single injection of E 2 into hypophysectomized eels failed in the induction of Vg synthesis. Similarly, E 2 alone was insufficient to induce Vg synthesis in the culture. On the other hand, the combination of E 2 with GH and/or PRL markedly stimulated Vg synthesis. Neither GH alone nor PRL alone had any effect on the induction of Vg synthesis by cultured hepatocytes. Hepatocytes isolated from E 2-primed eels also required GH or PRL for continuation of Vg synthesis. The highest Vg synthesis occurred at doses of 50 ng GH/ml and 1 μg PRL/ml in the presence of 2 × 10 -6 M E 2. These results indicate that the multihormonal stimulation of GH and/or PRL as well as E 2 is essential for the active synthesis of Vg in eels.

Effects of bovine growth hormone (GH) expression in transgenic mice on serum and pituitary immunoreactive mouse GH levels and pituitary GH-releasing factor binding sites

Pituitary and serum levels of homologous growth hormone (GH) and characteristics of specific GH-releasing factor (GHRF) binding to pituitary homogenates were examined in transgenic mice expressing bovine GH (bGH) gene regulated by different promoters [mouse metallothionein-I (MT) or phosphoenolpyruvate carboxykinase (PEPCK)] and in their normal littermates. Pituitary GH concentration and GHRF binding were reduced by approximately 50% in transgenic MT-bGH mice in which serum bGH levels were about 20 micrograms/l and by approximately 95% in transgenic PEPCK-bGH mice in which serum bGH levels were tenfold higher. Suppression of plasma immunoreactive mouse GH (mGH) levels was detected in MT-bGH but not in PEPCK-bGH animals, presumably due to cross-reaction of the antiserum employed with bGH. Scatchard plots of GHRF binding to washed homogenates of pituitary glands from normal and young adult MT-bGH transgenic mice were curvilinear, indicating the presence of two types of binding sites, with low and high affinities. Both types of binding sites were reduced in number in MT-bGH transgenic mice without changes in their affinity. In 5-7-month-old MT-bGH transgenic mice there were changes in pituitary GH levels, in GHRF binding levels and in characteristics of GHRF binding that closely resembled the alterations described previously in aging rats. We conclude that over-expression of heterologous GH genes in transgenic mice can lead to partial or virtually complete suppression of somatotroph function, depending on the levels of heterologous GH in the circulation, and that transgenic MT-bGH mice exhibit symptoms of remarkably early onset of neuroendocrine aging.

The Effect of Bovine Growth Hormone on Growth, Carcass Composition and Meat Quality of Dairy Heifers

Abstract Our objective was to examine the effects of bovine growth hormone (bGH) on growth, carcass composition and meat quality of dairy heifers. Nine monozygotic twin pairs of Friesian or Red Danish cattle were used, and pair-fed à diet consisting of grass silage, barley and soybean meal. Within each pair, one animal was given daily subcutaneous injections of 20 IU of pituitary-derived bGH (15–20 mg), while the other animal was injected with saline (excipient). Treatments started at 179±2 kg body weight and lasted for 15.6 weeks. At slaughter, carcass composition and meat quality were analyzed. bGH treatment increased gain by 8% (948 vs. 877 g/d; P <0.03). The amount of saleable meat in carcass and lean content of four main carcass cuts were on average increased by 2% (P <0.05). Concomitantly, carcass fat trim was reduced by 12% (P <0.001), fat trim of individual cuts by 4–21% (P <0.05), and kidney fat by 13% (P <0.01). Except for a 20% reduction of intramuscular fat content (P <0.001), meat quality assessed by objective as well as subjective methods was unaffected by bGH treatment. In summary, bGH treatment of dairy heifers around puberty stimulated growth and reduced carcass fattening including intramuscular fat, while eating quality of the meat was unaffected.

Metabolic Effects of Bovine Growth Hormone and Genetically Engineered Rainbow Trout Growth Hormone in Rainbow Trout (Oncorhynchus mykiss) Reared at a High Temperature

The growth promoting ability of bovine growth hormone purified from natural sources (bGH) and genetically engineered rainbow trout growth hormone (rtGH) were compared in rainbow trout (Oncorhynchus mykiss) reared at 17.0 °C. Fish were fed high (on-demand feeding) and low (2.8–4.6% of body weight/d) rations. On both rations, length specific growth rates were significantly higher in bGH treated fish than in all other treatments. No significant differences in weight specific growth rates were detected between treatments. Testosterone levels in fish fed the high ration and treated with 1.0 μg/g rtGH or bGH were significantly elevated compared with controls as were 17-β-estradiol levels in females. bGH significantly reduced condition factors of low ration fish, and bGH and rtGH significantly depressed hepatosomatic indicies of high ration fish compared with controls. In a second experiment, weight and length specific growth rates were higher in rtGH and bGH injected fish than in saline controls but these differences were not significant. DNA standardized RNA levels were higher in rtGH and bGH treated fish than in saline control fish and these differences were significant in bGH treated fish. Results indicate that at high rearing temperatures GH administration does not have a major influence on growth but does stimulate steroidogenic and metabolic activity.

The Simple Analytics of Technology Adoption: Bovine Growth Hormone and the Dairy Industry

AbstractEconomic simulation studies of the effects of bovine growth hormone (bGH) on the dairy industry usually assume that producers will have the incentive to adopt bGH and that aggregate milk supply will increase. Based on the description of per‐cow milk yield response to bovine growth hormone (bGH), a short‐run model of milk production is developed to analyze the farm‐level incentives to adopt bGH. This analysis emphasizes that the incentives to adopt a new technology greatly depend on how it alters the existing production environment. Because higher levels of energy are needed in the cow to attain greater levels of production made possible with bGH, those farmers who can most easily and inexpensively expand energy levels in the cow will be most likely to adopt. The model identifies: (1) why farmers may not have the incentive to adopt the new technology; and (2) if farmers adopt bGH, they may not have the economic incentive to produce at the levels obtained in test studies.

The effects of bovine growth hormone and thyroxine on growth rate and carcass measurements in lambs.

The effects of bovine growth hormone (GH) and thyroxine (T4) on growth and carcass characteristics were assessed in Dorset ram lambs. Lambs in four groups (n = 10/group) were treated for 30 d as follows: controls, 3.33 mg (6 IU) GH/d (s.c.); 5-mg T4 implant (s.c.) on d 1 and a 10-mg T4 implant 21 d later; GH + T4. Blood samples were collected at 3-d intervals for analysis of GH, T4, triiodothyronine, somatomedin-C and testosterone concentrations. Six lambs/group were slaughtered for carcass measurements and composition. Daily GH injections increased (P less than .005) baseline plasma GH levels 10-fold, whereas plasma T4 concentrations were increased 10% (P less than .10) by the implants. Somatomedin-C increased with time in all groups, but the increments from d 0 to d 30 were higher (P less than .05) with GH treatment. Average daily gain (mean = 352 g/d), feed consumption and feed to gain ratio were not affected (P greater than .1) by GH or T4 treatment in ram lambs. Hot carcass weight and dressing percentage were increased (P less than .05) by T4. Growth hormone increased carcass protein content (P less than .005) and muscle weights while reducing carcass fat (P less than .05). Carcass composition was not altered by T4 alone, and the T4 x GH interaction was not significant; however, the combination of T4 and GH resulted in greater muscle and protein weight than did either hormone alone or no hormone administration. There were no differences in bone length or in the metacarpal growth plate width among groups. The beneficial effects of GH on carcass composition were not further enhanced by administration of thyroxine.

Changes in protein metabolism of ovine primary muscle cultures on treatment with growth hormone, insulin, insulin-like growth factor I or epidermal growth factor.

Methods for the primary culture of muscle cells from fetal sheep were developed which gave high yields of cells. Myoblasts were grown in vitro, and allowed to fuse to form contractile multinucleate myotubes; these could be maintained in a good condition for at least 2 weeks. Protein turnover in these differentiated cultures was examined for sensitivity to each of four potentially anabolic peptide hormones and growth factors: insulin, insulin-like growth factor I (somatomedin C), epidermal growth factor and growth hormone. Insulin was found to have no effect except at high concentrations (1 mumol/l), compatible with its role as a somatomedin analogue. Insulin-like growth factor I was active at lower levels (1 nmol/l) but the cultures were not as responsive to it as were primary rat muscle cultures or differentiated L6 cells, which were tested in similar experiments. The maximum stimulation of protein synthesis observed with the ruminant system was only 16%. Epidermal growth factor was highly anabolic for primary cultures from sheep muscle, and the cells were very sensitive to it, half-maximal stimulation of protein synthesis being seen with concentrations as low as 20 pmol/l. No effects of bovine growth hormone were seen in the ovine system. However, an inhibition of protein breakdown was found with high concentrations (0.1 mumol/l) in the L6 rat myoblast cell line. It was found that the culture conditions used could affect the observed responses of protein synthesis and degradation, despite withdrawal of serum from the incubation media 22 h before testing.

Pre-pubertal mammogenesis in the sheep 3. The effects of restricted feeding or daily administration of bovine growth hormone and bromocriptine on mammary growth and morphology

ABSTRACTIn crossbred female lambs reared on a concentrate diet between 8 and 20 weeks of age, a restriction in food intake to 40 g/kg body weight per day decreased live-weight gain (155 g/day) compared with that in control lambs fed ad libitum (284 g/day) and significantly reduced final live weight and the size of the mammary fat pad (P &lt; 0·001). However, restricted lambs at 20 weeks had more total parenchymal deoxyribonucleic acid (DNA; 54·7 v. 47·5 mg) occupying a greater mass of mammary fat pad (17·0 v. 13·2 g) than control lambs (P &gt; 0·10). Restricted feeding had little effect on mean plasma growth hormone (GH) concentrations at 12 and 18 weeks of age, but decreased plasma insulin and prolactin concentrations.In lambs fed ad libitum, daily subcutaneous (s.c.) injections of 0·1 mg bovine pituitary GH per kg live weight between 8 and 20 weeks of age significantly increased daily live-weight gain (347 g/day; P &lt; 0·001) and also increased total mammary parenchymal DNA (71·2 mg; P &lt; 0·10) and the mass of fat pad occupied by parenchymal tissue (20·6 g; P &lt; 0·05), compared with the control treatment. Daily s.c. injection of bromocriptine (1 mg/day) had no effect on either body or mammary growth, but tended to reduce the effects of bovine GH when given in combination. Secretory activity was observed in the parenchymal tissue of the eight lambs receiving bovine GH alone, and also in five control lambs and three lambs receiving bromocriptine alone. Three lambs that had attained puberty by 20 weeks of age had the poorest mammary development of their respective treatment groups.Mammary gland development at 20 weeks of age was significantly correlated across treatment means with plasma GH concentrations estimated at 18 weeks of age (r = 0·95; P &lt; 0·05), but no correlations of similar magnitude were found between individuals within treatments at 20 weeks. Strongest correlations were found among 8-week-old lambs, where mammary parenchymal DNA was positively correlated with mean plasma GH (r = 0·62) and the GH:insulin ratio (r = 0·79) and negatively correlated with the prolactin:GH ratio (r = -0·65).

Effect of Dose of Bovine Growth Hormone on Milk Composition: α-Lactalbumin, Fatty Acids, and Mineral Elements1,2

Tissue-specific effects of bovine growth hormone on lactating dairy cows were examined by analysis of milk composition. Milk samples were from 6 cows that received subcutaneous injections of 0, 5, 10, 25, 50, and 100 IU/d of growth hormone in a Latin-square design. Samples from the last 5 d of each 10-d treatment period were pooled for analyses of milk components. Concentration of α-lactalbumin in milk increased progressively across the treatment range up to 32% above controls (1.30 mg/nl) at the 100 IU dose. Specific α-lactalbumin synthesis (expressed as a percent of total milk protein) was also increased. Secretion of de novo synthesized fatty acids (short and medium chain length) in milk was increased, but response plateaued between the 50 and 100IU/d. Secretion of preformed (long-chain) fatty acids progressively increased across the entire dose range. Thus, the percentage of long-chain fatty acids in milk increased at the highest doses of hormone. Changes in fatty acid composition of milk were apparently related to energy status; the milk response to 50 and 100IU/d of growth hormone caused cows to be in or near negative energy balance. Exogenous growth hormone did not affect the concentration of calcium, phosphorus, sodium, iron, copper, and manganese in milk. Results are consistent with growth hormone functioning in homeorhesis to coordinate the partitioning of all nutrients to support the increased secretion of milk and milk components.

“In Vitro” Effects of Bovine Growth Hormone on RNA Labelling in Brain and Liver Slices of Neonatal Hypothyroid Rats

The present studies were performed in order to analize the "in vitro" effects of bovine growth hormone upon the RNA labelling slices from cerebrum and liver of neonatal hypothyroid rats. The [3H]-uridine incorporation was significantly enhanced by bovine growth hormone in both tissues. The stimulation was higher in liver than in cerebrum. The present results confirm the direct action of growth hormone on the RNA synthesis in liver and cerebrum during the postnatal development of the rat.

Growth hormone increases neonatal mouse urine epidermal growth factor

The effects of bovine growth hormone (bGH) and triiodothyronine (T3), alone and in combination, were studied on urinary-EGF (U-EGF) in newborn mice. All three treatments significantly augmented the concentration of U-EGF. The effect was far greater for T3 than for bGH. No EGF response was seen in submandibular gland or kidney tissues suggesting that, in newborn animals, these hormones selectively modulate U-EGF.

Effects of bovine growth hormone on RNA synthesis in brain and liver of neonatal hypothyroid rats.

The action of growth hormone upon RNA synthesis was studied in isolated nuclei from cerebrum and liver of hypothyroid rats. The acute administration of bovine growth hormone (bGH) to cretinoid rats, 10 days after birth, stimulated the endogeneous activity of RNA polymerase I and II in both organs. The transcription of ribosomal RNA in cerebrum and hnRNA in liver increased 40 min. after the injection and continued to be higher than in controls until 14 hrs. An increase in the synthesis of hepatic ribosomal RNA occurred 5 hrs. after treatment, the effect persisting during the whole period studied. The activity of cerebral RNA polymerase II displayed a bimodal curve with an early stimulation at 40 min. and a second one at 14 hrs. The results give evidence in favour of the action of growth hormone during the postnatal development of rat brain.

Effects of bovine growth hormone on the retarded cerebral development induced by neonatal hydrocortisone intoxication.

In comparison with normal controls, hydrocortisone-intoxicated rats (HC rats) had smaller cerebra, lowered 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity, and greatly reduced learning ability. The reduction in cerebral weight and DNA content was considered to be caused by a decrease in the number of proliferating glial cells, because the usual postnatal elevation of thymidine kinase (TK) activity was found to be suppressed in the cerebra from the HC rats. Electron microscopic observation of the pituitary gland revealed that the 5-day-old HC rat contained growth hormone (GH) secretory cells which were fully packed with GH granules, suggesting a disorder in the system which releases GH. In an attempt to promote cerebral development in the HC rats, we administered bovine GH (bGH) to some of the HC rats daily from the day of birth until weaning (HC + bGH rats). In the HC + bGH rats, the cerebral DNA was restored to normal levels and a concomitant increase in TK and CNPase activity was noted. Furthermore, in the brightness discrimination test, whereas the HC + bGH rats attained the learning ability of the normal controls after only 10 sessions, the HC rats were unable to reach an equivalent level even after 25 sessions.

Effects of bovine growth hormone on plasma FFA concentrations and liver, muscle and carcass lipid content in rainbow trout, Salmo gairdneri Richardson

Bovine growth hormone (GH) given daily to rainbow trout, Sulmo gairdneri for 4 or 7 days at either 10.00 or 14.00 hours, significantly increased plasma free fatty acid (FFA) levels but had not effect on plasma cholesterol levels. Liver lipid content of the GH‐injected trout after seven injections was significantly lower than comparable controls in groups injected at both 10.00 and 14.00 hours. There were no apparent effects of GH on carcass or muscle lipid content although in fish injected and sampled at 14.00 hours there was a significant correlation between the number of injections and carcass lipid content.Changes in hepatosomatic index (HSI), liver, muscle and carcass lipid content, plasma FFA and cholesterol concentrations and somatotrop activity during food‐deprivation for up to 60 days are described. Despite significant decreases in liver and muscle lipid content and increases in plasma FFA levels in food‐deprived fish, there was no concomitant change in apparent somatotrop activity.The data are interpreted to indicate that although exogenous GH, in the doses used here, appears to stimulate mobilization of lipid reserves, particularly from the liver, there is no evidence that enforced changes in lipid reserves elicits a response of the endogenous somatotrop cells.