This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Quinton, N. D. Articles by Ross, R. J. M. Search for Related Content PubMed PubMed Citation Articles by Quinton, N. D. Articles by Ross, R. J. M.

Leptin Binding Activity Changes with Age: The Link between Leptin and Puberty¹

The Division of Clinical Sciences (N.D.Q., S.K.J., S.A.S., R.J.M.) and School of Health and Related Research (S.W.), Sheffield University; Biomedical Research Centre (N.D.Q., R.F.S., A.I.F.B.), Sheffield Hallam University; Endocrine Science Group (P.E.C., M.S.G.), University of Manchester; and The Christie Hospital (S.S.), Manchester, United Kingdom; and INSERM Unite 344 (M.-C.P.-V.), Faculte de Medicine Necker, 75730 Paris Cedex 15, France

Address all correspondence and requests for reprints to: Dr. R. J. M. Ross, Department of Medicine/Clinical Sciences, Northern General Hospital, Sheffield S5 7AU, United Kingdom and Dr. P. E. Clayton, Royal Manchester Children’s Hospital, Pendlebury, Manchester M27 4HA, United Kingdom. E-mail R.J.Ross{at}Sheffield.ac.uk

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
The timing of the physical transition from child to adult is determined by a biological clock that switches off the pituitary gonadal axis during infancy until puberty. Body composition (and in particular, fat mass), through leptin, are critical signals to this clock. However, no direct relationship between leptin and puberty has been demonstrated. Leptin is bound in the circulation by a high-affinity binding protein, which has been identified as a soluble leptin receptor. We found circulating levels of leptin binding activity (LBA) to be low at birth, to be high in the prepubertal years, to fall through puberty, and then to remain stable during adult life. LBA correlated with pubertal status in both boys and girls. We postulate that the fall in LBA, associated with increasing age and puberty, reflects a reduction in expression of truncated leptin receptors, and leptin is then available to the full-length receptor, which transmits the biological signal for leptin. The high levels of LBA occur during the years when the pituitary gonadal axis is quiescent. Thus, the change in LBA could explain how leptin regulates puberty.

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
PUBERTY, the transition from child to adult is the result of reactivation of the pituitary gonadal axis. Sex steroids reach adult levels in late gestation, driving sexual differentiation in the fetus, then (shortly after birth) the pituitary gonadal axis switches off and lies dormant until the onset of puberty. We are now beginning to define some of the metabolic switches that program this biological clock. The importance of body composition has been recognized since the 1970s, when Frisch (1) suggested that it was necessary for women to maintain a specific percentage of body fat to achieve menarche and fertility. The recent cloning of the obesity gene and characterization of its product leptin, which is secreted from fat cells, has provided us with a signaling system whereby energy stores are sensed by physiological systems. It is now clear that leptin has a much wider role in human metabolism than just the regulation of body fat mass (2, 3).

Leptin acts through a class 1 cytokine receptor, the leptin receptor, which is highly expressed in the hypothalamus (4, 5). The biological actions of leptin include the regulation of appetite and energy expenditure, as well as involvement in the control of the hypothalamic-pituitary-gonadal axis (2, 3). In rodents, leptin administration accelerates the onset of reproductive function and restores fertility in the mutant ob/ob mouse (6, 7). Two recent reports of humans with mutations in the leptin receptor and leptin gene, who failed to progress through puberty, provide important evidence for the role of leptin in facilitating pubertal development (8, 9). However, the link between puberty and leptin is not fully established. Cross-sectional and longitudinal studies of leptin levels before and during puberty indicate that leptin levels follow changes in fat mass (10, 11, 12), although a brief pulse of leptin may precede the onset of puberty in males (13). In children, age is also an independent determinant of leptin levels, and leptin may act as a permissive signal to puberty over time (12).

Binding proteins for circulating leptin have been described in both the human and rodents (14, 15, 16). Varying sizes of the binding protein have been reported but would be compatible with the size of the extracellular domain of the leptin receptor (14, 15). In humans, the leptin-binding protein can be precipitated by a leptin receptor antibody (14). In the pregnant mouse, the binding protein has been sequenced and confirmed as the extracellular domain of the leptin receptor (17), and expression of the extracellular domain of the human leptin receptor in COS7 cells results in the production of a binding protein in the medium (6). These results are consistent with observations made for other members of the class I cytokine family of receptors, a number of which produce soluble receptors that represent the extracellular domain of the receptor (18).

Leptin-binding protein [or leptin binding activity (LBA)] has only been measured in limited clinical situations. In the studies performed, LBA was lower in obese patients, compared with lean, suggesting that the obese have higher free levels of leptin (14, 15, 16). We have modified an assay for GH-binding protein (GHBP) to measure LBA (19). The assay specifically measures a high-affinity binding protein; and using this assay, we have measured levels of LBA through the ages from birth to old age. The results show that the major change in LBA occurs at puberty.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
LBA assay

Stripping of leptin from serum sample. To 200 µL of serum, 500 µL of prechilled 2% Norit A charcoal (American Norit Co., Atlanta, GA) 0.2% Dextran T70 (Amersham Life Science, Buckinghamshire, UK) in assay buffer was added at room temperature, vortex mixed, and immediately placed on ice for 5 min. The sample was centrifuged at 4 C for 12 min at 10,000 x g. The supernatant (stripped of free leptin) was removed by pipette and placed in a new tube.

Measurement of LBA. Fifty microliters of stripped serum was incubated with 150 µL assay buffer (0.01 mol/L phosphate buffer (pH 7.4), 0.18 mol/L MgCl₂, 1% BSA), 100 µL [¹²⁵I]Leptin [135 µCi/µg (Linco Research, Inc., St. Louis, MO)], in the presence (nonspecific) or absence (total binding) of 1 µg unlabeled leptin (R&D Systems, Abingdon, Oxford, UK). For separation of bound from unbound, 1 mL prechilled 2% charcoal-0.2% Dextran T70 slurry in assay buffer was added to the overnight incubation, vortexed, placed on ice for 10 min, and centrifuged at 4 C for 12 min at 10,000 x g. One milliliter of the supernatant was aspirated by pipette and counted in an automatic -counter. The specific binding (total binding minus nonspecific binding) obtained was expressed as a percentage of the total [¹²⁵I]Leptin counts per minute incubated in 50 µL of serum and called the LBA. All samples were measured in duplicate.

Serum samples with high and low levels of LBA were used as control serum and were run in each assay at the beginning and end of the assay.

High-performance liquid chromatography (HPLC) analysis

The HPLC method was developed from a method used to measure GH-BP by Tar et al. (20). HPLC separations were performed using a liquid chromatograph (model 600, Waters Corp., Milford, MA) equipped with a sample injector (model U6K) fitted with a 250-µL loop and an analytical Protein Pak 300sw column (Waters; 0.75 x 30 cm). Absorbance at 280 nm was monitored with an LC spectrophotometer (Waters), and radioactivity was recorded on-line using a Bertold LB 504 -detector (E G and G, Evry, France) connected to a Compaq computer.

Serum (150 µL) was incubated overnight at 4 C with 30 µL assay buffer and 20 µL [¹²⁵I]Leptin. A parallel incubation was carried out in the presence of an excess of unlabeled leptin (2 µg). After filtration through a 0.45-µm minifilter Millipore Corp. (Watford, UK), the entire incubation was placed onto an HPLC Protein Pak 300sw column. Elution was performed autocratically using a degassed buffer (0.1 mol/L Na₂SO₄ and 0.1 mol/L potassium phosphate, pH 7.0) pumped at a rate of 0.5 mL/min.

Leptin measurement

Human leptin concentrations were measured in duplicate using a specific Human Leptin RIA kit (Linco Research, Inc.) with an interbatch variation of between 3.0 and 6.0% and a detection limit of 0.5 ng/mL.

Statistics

Statistical analysis was performed using the software package SPSS. Pearson product-moment correlations were calculated to test association among variables. One-way ANOVA was used to investigate the effect of pubertal status on LBA. The t test, with Bonferroni adjusted P values, was used to look for differences between groups. A stepwise multiple-regression analysis with a P value less than 0.05 for entry and less than 0.10 for removal was used to determine which of the following possible explanatory variables [age, puberty, body mass index (BMI), and leptin] could be used to predict LBA in boys and girls.

Serum samples

All children and adults gave informed written consent or assent, and the studies had the approval of the local research ethics committees. Serum samples were taken between 0900 and 1000 h, and neonatal samples were from umbilical cord blood. Samples were separated and stored at -20 C until analysis. Pubertal staging was performed by an experienced pediatrician using the Tanner stages of puberty. Clinical details are given in Table 1.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

Competition experiments. Displacement curves with serial dilutions of neat stripped serum showed parallel displacement. Specificity for leptin was confirmed by incubation with unlabeled human GH and interleukin-6 (Fig. 1A), which showed no displacement. Scatchard analysis of competition experiments with human leptin showed a linear plot with a binding affinity of 1.0–1.4 x 10⁹ mol/L^-1 (Fig. 1B).

View larger version (11K): [in this window] [in a new window]   Figure 1. A, Hormonal specificity of binding of [125I]Leptin to normal human serum. The specific binding of [125I]Leptin is expressed as a percentage of the maximal binding. Values are the mean of duplicate determinations from a representative experiment. IL-6, Interleukin-6. B, Scatchard analysis of [125I]Leptin to normal human serum. B/F, Bound/Free. C, Elution profile of [125I]Leptin incubated with human serum. [125I]Leptin (4 x 104 cpm) was incubated with 150 µL serum without (thick line) and with (thin line) excess of native leptin. Binding was expressed as the radioactivity in the first peak over the radioactivity in peak 1 and peak 2 (free [125I]Leptin. For the profile shown, total binding was 29.0%, and nonspecific 13.1%, radioactivity.

The assay had a sensitivity of 0.6% specific binding (mean + 2 SD of 10 repeated measurements with zero sample). At 12 and 6% specific binding, the intraassay coefficient of variation was 3.2 and 4.1%, and the interassay coefficient of variation was 6.4 and 4.8%, respectively.

Results from this assay were compared with those obtained by HPLC. A single profile is shown in Fig. 1C. HPLC revealed a peak at the appropriate size for a soluble receptor (85 kDa). Results of specific binding were comparable, considering the different methodolgy for the eight samples analyzed; mean ± SEM for LBA 10.5 ± 1.07% vs. HPLC 9.4 ± 0.78%. A comparison of samples analyzed is summarized in Table 2; these have been corrected to allow for the difference in sample volume used in the two assays.

Figure 2 shows the median LBA at the different ages of life. LBA was lowest at birth, highest in prepubertal children, and fell during puberty to a mean level of between 7 and 9% in young men and women and remained at this level through to old age. There were no differences in LBA between males and females at any age.

View larger version (32K): [in this window] [in a new window]   Figure 2. LBA through the ages from birth to the elderly.

View larger version (18K): [in this window] [in a new window]   Figure 3. LBA against: age (A), pubertal status (B), and testicular volume (C).

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
Circulating soluble receptors are a feature of a number of members of the cytokine family of receptors (18). The most widely studied, with respect to the endocrine system, is the GHBP, which is derived (by proteolytic cleavage) from the extracellular domain of the GH receptor (21). In most studies, GHBP levels reflect the tissue-specific expression of the GH receptor; and recently, a truncated form of the receptor has been identified that generates large amounts of GHBP and acts as a dominant negative antagonist of GH signaling (22, 23). The leptin receptor gene is expressed as a number of alternatively spliced isoforms (Ob-Ra to Ob-Re) (24, 25) of which Ob-Ra, b, and e are the major splice forms (26). Ob-Rb contains all elements for signaling, Ob-Ra has a truncated cytoplasmic domain, and Ob-Re is truncated at the extracellular domain, which, when expressed in transfection studies, generates an LBA (6). The finding of a fall in high-affinity LBA may reflect a change in expression of truncated leptin receptors, and this may result in more free leptin being available at the hypothalamus, which expresses Ob-Rb, the full-length signaling leptin receptor.

We have validated an assay for measuring LBA in human serum. The assay is based on a method previously described for the measurement of GH-binding protein activity (19). The LBA assay was specific, reproducible, and sensitive. It detected a high-affinity binding protein, Ka 1.0–1.4 x 10⁹ M^-1, which would be compatible with the expected affinity of the soluble receptor (6). Results from this assay were comparable with HPLC analysis of leptin-binding protein. Scatchard analysis suggested that the assay detected a single species of binding protein, although there may be lower-affinity leptin-binding proteins that were not detected by this assay (14). LBA has been reported to relate inversely to leptin levels; however, this may have been an artefact caused by interference in the assay by endogenous leptin (16). In the present study, endogenous leptin was removed before assaying LBA, and no statistical evidence of a relationship was found between leptin levels and binding activity except in girls. In girls, leptin increases with age and puberty as LBA is decreasing. The negative correlation would therefore be expected.

LBA was low at birth, high in early childhood, fell during puberty, and remained at the postpubertal level throughout adult life. These changes in LBA parallel the known changes in activity of the pituitary gonadal axis, with high levels of LBA being present during the childhood years, when the pituitary gonadal axis is quiescent. There was no difference between boys and girls or men and women in LBA. In pubertal children, LBA showed a significant relationship with age, pubertal status, BMI, and testicular volume in boys. Multivariate analysis suggested that the most important factor was age. There is an absolute requirement for leptin for the initiation and progression of puberty, as demonstrated by the hypogonadal state of leptin-resistant or -deficient human subjects (8, 9). However, leptin may only provide a tonic background signal on which other initiators act, because leptin levels in puberty primarily relate to fat mass (2). Our finding, of the direct inverse relationship between LBA and pubertal status or age, with a fall in LBA seen at the earliest stages of puberty, suggests that this is a link from leptin to the progression of puberty.

In adult subjects, there were no differences in LBA between the sexes. This is in sharp contrast to the well-recognized sexual dimorphism in serum leptin levels (3). If the change in LBA is related to a change in leptin receptor subtype, then this may be an alteration that occurs at puberty and remains unaltered through adult life. We found no relationship between BMI and LBA in adults, although our studies were confined to a normal population. Previous studies have suggested that LBA is reduced in obesity (14, 15, 16).

In conclusion, we have developed a simple and specific assay for the measurement of LBA. This assay demonstrates an inverse relationship between age and LBA and a strong correlation between puberty and a fall in LBA. The fall in the earliest stages of puberty suggests that this is a primary event, not driven by changes in sex steroids. The fall in LBA could be explained by a change in leptin receptor expression, which may be the link between leptin and puberty.

	Footnotes

 
¹ This work was supported by The Northern General Hospital Research Committee, the Biomedical Research Centre at Sheffield Hallam University, The YCRC, Trent Regional Research Schemes, The British Council Alliance Scheme, and Serono Laboratories, Inc.

Received October 28, 1998.

Revised March 16, 1999.

Accepted March 28, 1999.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Frisch R, Revelle R. 1970 Height and weight at menarche and a hypothesis of critical body weights and adolescent events. Science. 169:397–399.[Abstract/Free Full Text]
2. O’Rahilly S. 1998 Life without leptin. Nature. 393:330–331.
3. Rosenbaum M, Leibel RL. 1998 Leptin: a molecule integrating somatic energy stores, energy expenditure, and fertility. Trends Endocrinol Metab. 9:117–124.
4. Zhang Y, Proenca R, Maffei M, Barone M, Leopold L, Friedman JM. 1994 Positional cloning of the mouse obese gene and its human homologue. Nature. 372:425–432.[CrossRef][Medline]
5. Tartaglia LA, Dembski M, Weng X, et al. 1995 Identification and expression cloning of a leptin receptor, OB-R. Cell. 83:1263–1271.[CrossRef][Medline]
6. Liu C, Liu X, Barry G, Ling N, Maki RA, DeSouza EB. 1997 Expression and characterization of a putative high affinity human soluble leptin receptor. Endocrinology. 138:3548–3554.[Abstract/Free Full Text]
7. Ahima RS, Dushay J, Flier SN, Prabakaran D, Flier JS. 1997 Leptin accelerates the onset of puberty in normal female mice. J Clin Invest. 99:391–395.[Medline]
8. Clement K, Vaisse C, Lahlous N, et al. 1998 A mutation in the human leptin receptor gene causes obesity and pituitary dysfunction. Nature. 392:398–401.[CrossRef][Medline]
9. Strobel A, Issad T, Camoin L, Ozata M, Stosberg AD. 1998 A leptin missense mutation associated with hypogonadism and morbid obesity. Nat Genet. 18:213–215.[CrossRef][Medline]
10. Blum WF, Englaro P, Hanitsch S, et al. 1997 Plasma leptin levels in healthy children and adolescents: dependence on body mass index, body fat mass, gender, pubertal stage, and testosterone. J Clin Endocrinol Metab. 82:2904–2910.[Abstract/Free Full Text]
11. Garcia-Mayor RV, Andrade MA, Rios M, Lage M, Dieguez C, Casanueva FF. 1997 Serum leptin levels in normal children: relationship to age, gender, body mass index, pituitary-gonadal hormones, and pubertal stage. J Clin Endocrinol Metab. 82:2849–2855.[Abstract/Free Full Text]
12. Clayton PE, Gill MS, Hall CM, Tillmann V, Whatmore AJ, Price DA. 1997 Serum leptin through childhood and adolescence. Clin Endocrinol (Oxf). 46:727–733.[CrossRef][Medline]
13. Mantzoros CS, Flier JS, Rogol AD. 1997 A longitudinal assessment of hormonal and physical alterations during normal puberty in boys vs. rising leptin levels may signal the onset of puberty. J Clin Endocrinol Metab. 82:1066–1070.[Abstract/Free Full Text]
14. Sinha MK, Opentanova I, Ohannesian JP, et al. 1996 Evidence of free and bound leptin in human circulation. J Clin Invest. 98:1277–1282.[Medline]
15. Houseknecht KL, Mantzoros CS, Kuliawat R, Hadro E, Flier JS, Kahn BB. 1996 Evidence for leptin binding to proteins in serum of rodents and humans: modulation with obesity. Diabetes. 45:1638–1643.[Abstract]
16. Diamond Jr FB, Eichler DC, Duckett G, Jorgensen EV, Shulman D, Root AW. 1997 Demonstration of a leptin binding factor in human serum. Biochem Biophys Res Commun. 233:818–822.[CrossRef][Medline]
17. Garilova O, Barr V, Marcus-Samuels B, Reitman M. 1997 Hyperleptinemia of pregnancy associated with the appearance of a circulating form of the leptin receptor. J Biol Chem. 272:30546–30551.[Abstract/Free Full Text]
18. Muller-Newen G, Kohne C, Heinrich PC. 1996 Soluble receptors for cytokines and growth factors. Int Arch Allergy Immunol. 111:99–106.[Medline]
19. Amit T, Barkey RJ, Youdim MBH, Hochberg Z. 1990 A new and convenient assay of growth hormone-binding protein activity in human serum. J Clin Endocrinol Metab. 71:474–479.[Abstract]
20. Tar A, Hocquette J, Souberbielle J, Clot J, Brauner R, Postel-Vinay MC. 1990 Evaluation of the growth hormone-binding proteins in human plasma using high pressure liquid chromatography gel filtration. J Clin Endocrinol Metab. 71:1202–1207.[Abstract]
21. Baumann G. 1994 Growth hormone-binding proteins: state of the art. J Endocrinol. 141:1–6.[Abstract/Free Full Text]
22. Dastot F, Sobrier F, Duquesnoy P, Duriez B, Goosens M, Amselem S. 1996 Alternatively spliced forms in the cytoplasmic domain of the human growth hormone (GH) receptor regulate its ability to generate a soluble GH-binding protein. Proc Natl Acad Sci USA. 93:10723–10728.[Abstract/Free Full Text]
23. Ross RJM, Esposito N, Shen XY, et al. 1997 A short isoform of the human growth hormone receptor functions as a dominant negative inhibitor of the full length receptor and generates large amounts of binding protein. Mol Endocrinol. 11:265–273.[Abstract/Free Full Text]
24. Chen H, Charlat O, Tartaglia LA, et al. 1996 Evidence that the diabetes gene encodes the leptin receptor: identification of a mutation in the leptin receptor gene in db/db mice. Cell. 84:491–495.[CrossRef][Medline]
25. Lee G, Proenca R, Montez JM, et al. 1996 Abnormal splicing of the leptin receptor in diabetic mice. Nature. 379:632–635.[CrossRef][Medline]
26. Lollmann B, Gruninger S, Stricker-Krongrad A, Chiesi M. 1997 Detection and quantification of the leptin receptor splice variants Ob-a, b, and, e in different mouse tissues. Biochem Biophys Res Commun. 238:648–652.[CrossRef][Medline]

This article has been cited by other articles:

				W. Pan, H. Hsuchou, H. Tu, and A. J. Kastin Developmental Changes of Leptin Receptors in Cerebral Microvessels: Unexpected Relation to Leptin Transport Endocrinology, March 1, 2008; 149(3): 877 - 885. [Abstract] [Full Text] [PDF]

				R. Brauner, C. Trivin, M. Zerah, J.-C. Souberbielle, F. Doz, C. Kalifa, and C. Sainte-Rose Diencephalic Syndrome due to Hypothalamic Tumor: A Model of the Relationship between Weight and Puberty Onset J. Clin. Endocrinol. Metab., July 1, 2006; 91(7): 2467 - 2473. [Abstract] [Full Text] [PDF]

				G. K Bhat, T. M Plant, and D. R Mann Relationship between serum concentrations of leptin, soluble leptin receptor, testosterone and IGF-I, and growth during the first year of postnatal life in the male rhesus monkey, Macaca mulatta Eur. J. Endocrinol., July 1, 2005; 153(1): 153 - 158. [Abstract] [Full Text] [PDF]

				J. Kratzsch, C. Schubring, B. Stitzel, A. Bottner, A. Berthold, J. Thiery, and W. Kiess Inverse Changes in the Serum Levels of the Soluble Leptin Receptor and Leptin in Neonates: Relations to Anthropometric Data J. Clin. Endocrinol. Metab., April 1, 2005; 90(4): 2212 - 2217. [Abstract] [Full Text] [PDF]

				J. T Smith, P. J Mark, and B. J Waddell Developmental increases in plasma leptin binding activity and tissue Ob-Re mRNA expression in the rat J. Endocrinol., March 1, 2005; 184(3): 535 - 541. [Abstract] [Full Text] [PDF]

				D.A. Zieba, M. Amstalden, S. Morton, M.N. Maciel, D.H. Keisler, and G.L. Williams Regulatory Roles of Leptin at the Hypothalamic-Hypophyseal Axis Before and after Sexual Maturation in Cattle Biol Reprod, September 1, 2004; 71(3): 804 - 812. [Abstract] [Full Text] [PDF]

				K. J. Schulze, K. O. O'Brien, E. L. Germain-Lee, S. L. Booth, A. Leonard, and B. J. Rosenstein Calcium Kinetics Are Altered in Clinically Stable Girls with Cystic Fibrosis J. Clin. Endocrinol. Metab., July 1, 2004; 89(7): 3385 - 3391. [Abstract] [Full Text] [PDF]

				H. Zarkesh-Esfahani, A. G. Pockley, Z. Wu, P. G. Hellewell, A. P. Weetman, and R. J. M. Ross Leptin Indirectly Activates Human Neutrophils via Induction of TNF-{alpha} J. Immunol., February 1, 2004; 172(3): 1809 - 1814. [Abstract] [Full Text] [PDF]

				M. E. Wilson, J. Fisher, K. Chikazawa, R. Yoda, A. Legendre, D. Mook, and K. G. Gould Leptin Administration Increases Nocturnal Concentrations of Luteinizing Hormone and Growth Hormone in Juvenile Female Rhesus Monkeys J. Clin. Endocrinol. Metab., October 1, 2003; 88(10): 4874 - 4883. [Abstract] [Full Text] [PDF]

				D. R. Mann, A. O. K. Johnson, T. Gimpel, and V. D. Castracane Changes in Circulating Leptin, Leptin Receptor, and Gonadal Hormones from Infancy until Advanced Age in Humans J. Clin. Endocrinol. Metab., July 1, 2003; 88(7): 3339 - 3345. [Abstract] [Full Text] [PDF]

				N. Kado, J. Kitawaki, H. Koshiba, H. Ishihara, Y. Kitaoka, M. Teramoto, and H. Honjo Relationships between the serum levels of soluble leptin receptor and free and bound leptin in non-pregnant women of reproductive age and women undergoing controlled ovarian hyperstimulation Hum. Reprod., April 1, 2003; 18(4): 715 - 720. [Abstract] [Full Text] [PDF]

				M. Weise, G. Eisenhofer, and D. P. Merke Pubertal and Gender-Related Changes in the Sympathoadrenal System in Healthy Children J. Clin. Endocrinol. Metab., November 1, 2002; 87(11): 5038 - 5043. [Abstract] [Full Text] [PDF]

				J. Kratzsch, A. Lammert, A. Bottner, B. Seidel, G. Mueller, J. Thiery, J. Hebebrand, and W. Kiess Circulating Soluble Leptin Receptor and Free Leptin Index during Childhood, Puberty, and Adolescence J. Clin. Endocrinol. Metab., October 1, 2002; 87(10): 4587 - 4594. [Abstract] [Full Text] [PDF]

				K. Lin-Su, M. G. Vogiatzi, and M. I. New Body Mass Index and Age at Menarche in an Adolescent Clinic Population Clinical Pediatrics, September 1, 2002; 41(7): 501 - 507. [Abstract] [PDF]

				Z. Wu, M. Bidlingmaier, C. Liu, E. B. De Souza, M. Tschop, K. M. Morrison, and C. J. Strasburger Quantification of the Soluble Leptin Receptor in Human Blood by Ligand-Mediated Immunofunctional Assay J. Clin. Endocrinol. Metab., June 1, 2002; 87(6): 2931 - 2939. [Abstract] [Full Text] [PDF]

				N. Lahlou, T. Issad, Y. Lebouc, J.-C. Carel, L. Camoin, M. Roger, and J. Girard Mutations in the Human Leptin and Leptin Receptor Genes as Models of Serum Leptin Receptor Regulation Diabetes, June 1, 2002; 51(6): 1980 - 1985. [Abstract] [Full Text] [PDF]

				M. Maamra, M. Bidlingmaier, M.-C. Postel-Vinay, Z. Wu, C. J. Strasburger, and R. J. M. Ross Generation of Human Soluble Leptin Receptor by Proteolytic Cleavage of Membrane-Anchored Receptors Endocrinology, October 1, 2001; 142(10): 4389 - 4393. [Abstract] [Full Text] [PDF]

				S.M. Laird, N.D. Quinton, B. Anstie, T.C. Li, and A.I.F. Blakemore Leptin and leptin-binding activity in women with recurrent miscarriage: correlation with pregnancy outcome Hum. Reprod., September 1, 2001; 16(9): 2008 - 2013. [Abstract] [Full Text] [PDF]

				T K Hytinantti, M Juntunen, H A Koistinen, V A Koivisto, S-L Karonen, and S Andersson Postnatal changes in concentrations of free and bound leptin Arch. Dis. Child. Fetal Neonatal Ed., September 1, 2001; 85(2): F123 - 126. [Abstract] [Full Text] [PDF]

				L. Ghizzoni, G. Mastorakos, M. Ziveri, M. Furlini, A. Solazzi, A. Vottero, and S. Bernasconi Interactions of Leptin and Thyrotropin 24-Hour Secretory Profiles in Short Normal Children J. Clin. Endocrinol. Metab., May 1, 2001; 86(5): 2065 - 2072. [Abstract] [Full Text]

				E. Terasawa and D. L. Fernandez Neurobiological Mechanisms of the Onset of Puberty in Primates Endocr. Rev., February 1, 2001; 22(1): 111 - 151. [Abstract] [Full Text]

				N. Anim-Nyame, C. Domoney, N. Panay, J. Jones, J. Alaghband-Zadeh, and J.W.W. Studd Plasma leptin concentrations are increased in women with premenstrual syndrome Hum. Reprod., November 1, 2000; 15(11): 2329 - 2332. [Abstract] [Full Text] [PDF]

				A. D. Mooradian, R. Hurd, J. Chehade, K. Pun, and M. J. Haas Age-Related Changes in Plasma Leptin Binding Activity in Rats: A Comparison of a Simple Acid-Ethanol Precipitation Technique with Column Chromatography Experimental Biology and Medicine, September 1, 2000; 224(4): 273 - 277. [Abstract] [Full Text]

				P E CLAYTON and J A TRUEMAN Leptin and puberty Arch. Dis. Child., July 1, 2000; 83(1): 1 - 4. [Full Text]

This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Quinton, N. D. Articles by Ross, R. J. M. Search for Related Content PubMed PubMed Citation Articles by Quinton, N. D. Articles by Ross, R. J. M.