Specific monoclonal antibodies and ultrasensitive immunoassays for 20K and 22K human growth hormone

Different isoforms of growth hormone (20 kD-GH and 22 kD-GH) shows different biological activities in mesenchymal stem cell (MSC)

There are two main types of growth hormone (GH) in the circulatory system. One is 22 kD-GH, which is the predominant isoform in the circulating system, 90% GH is present as a 22 kD protein, and 10% of GH is present as a 20 kD protein. Amino acid sequences are identical between 20 kD-GH and 22 kD-GH protein, except that 20 kD-GH lacks 15 amino acid residues 32 to 46. Studies have shown that GH has many important biological effects on mesenchymal stem cells (MSCs). However, so far, the cellular characteristics of the two types of GH have not been studied in BM-MSCs. Furthermore, the biological activity of 20 kD-GH has not been explored in BM-MSCs. For this, in the current work, BM-MSCs were used as in vitro cell model. We have carried out the current research using a series of experimental techniques (such as Western-blot and indirect immunofluorescence). Firstly, we explored the cell behavior of two types of GH in the Bm-MSC model and found that they showed different biological characteristics; Secondly, we investigated the biological characteristics of 20 kD-GH and 22 kD-GH, and results showed that 22 kD-GH and 20 kD-GH exhibited different signaling profiles; Thirdly, we found that the 20 kD-GH and 22 kD-GH Gexhibited different regulatory effects on the osteogenic differentiation of BM-MSCs. The current research lays a solid foundation for further studies on the regulatory effects of GH on MSCs.

Short and Long-Term Effects of Growth Hormone in Children and Adolescents With GH Deficiency

The syndrome of impaired GH secretion (GH deficiency) in childhood and adolescence had been identified at the end of the 19^th century. Its non-acquired variant (naGHD) is, at childhood onset, a rare syndrome of multiple etiologies, predominantly characterized by severe and permanent growth failure culminating in short stature. It is still difficult to diagnose GHD and, in particular, to ascertain impaired GH secretion in comparison to levels in normally-growing children. The debate on what constitutes an optimal diagnostic process continues. Treatment of the GH deficit via replacement with cadaveric pituitary human GH (pit-hGH) had first been demonstrated in 1958, and opened an era of therapeutic possibilities, albeit for a limited number of patients. In 1985, the era of recombinant hGH (r-hGH) began: unlimited supply meant that substantial long-term experience could be gained, with greater focus on efficacy, safety and costs. However, even today, the results of current treatment regimes indicate that there is still a substantial fraction of children who do not achieve adult height within the normal range. Renewed evaluation of height outcomes in childhood-onset naGHD is required for a better understanding of the underlying causes, whereby the role of various factors - diagnostics, treatment modalities, mode of treatment evaluation - during the important phases of child growth - infancy, childhood and puberty - are further explored.

An update on clinical care for pregnant women with acromegaly

INTRODUCTION

As pregnancy is rare in women with acromegaly, only case reports and few series have been published.

AREAS COVERED

All case reports and publications dealing with pregnancy in patients with acromegaly were collated. Information concerning the effects of acromegaly on pregnancy outcomes, the impact of pregnancy on GH/IGF-I measurements, acromegaly comorbidity and pituitary adenoma size, the effects of treatment of acromegaly on fetus outcomes were retrieved and analyzed.

EXPERT COMMENTARY

Based on the small number of reported cases, pregnancy is generally uneventful, except for a potential increased incidence of gestational hypertension and diabetes mellitus. Medical therapy of acromegaly (dopamine agonists, somatostatin analogs, growth hormone-receptor antagonists) is generally interrupted before or at diagnosis of pregnancy. In very rare patients with a pituitary adenoma, particularly a macroadenoma that has not been surgically treated before pregnancy, or if a surgical remnant persists, or when acromegaly is revealed during pregnancy, tumor volume may increase and cause symptoms through a mass effect. Close monitoring of clinical manifestations and imaging are necessary during pregnancy in these cases. In the rare cases of symptomatic tumor enlargement during pregnancy, medical treatment with dopamine agonists or eventually somatostatin analogs may be attempted before resorting to transsphenoidal surgery.

Cellular internalization and trafficking of 20 KDa human growth hormone

Twenty kilodalton human growth hormone (20K-GH) is the second most abundant GH isoform after the twenty-two kilodalton human growth hormone (22 K-GH) isoform. 20K-GH exhibits similar but not identical physiological activities as that of 22K-GH. The cell behaviour of 22K-GH has been extensively studied, but little or no information has been reported regarding 20K-GH. Here, we focussed on the internalization of 20K-GH. We found that the internalization of 20K-GH is rapid and occurs in a time- and dose-dependent manner. 20K-GH internalization is mediated by GHR. It appears that the internalization of 20K-GH and GHR into the cytoplasm is mediated by clathrin and/or caveolin. The current study indicates that 20K-GH can internalize into the cytoplasm and suggests that the internalized 20K-GH may exhibit different functions from those of 22K-GH.

MANAGEMENT OF ENDOCRINE DISEASE: Acromegaly and pregnancy: a contemporary review

Although fertility is frequently impaired in women with acromegaly, pregnancy is apparently becoming more common due to improvement in acromegaly treatment as well as in fertility therapy. As a result, several studies on pregnancy in patients with acromegaly have been published in recent years adding new and relevant information to the preexisting literature. Also, new GH assays with selective specificities and the knowledge of the expression of the various GH genes have allowed a better understanding of somatotrophic axis function during pregnancy. In this review, we show that pregnancy in women with acromegaly is generally safe, usually with tumoral and hormonal stability. Although the paucity of data limits evidence-based recommendations for preconception counseling and pregnancy surveillance, controlling tumor size and hormonal activity before pregnancy is highly recommended to ensure better outcomes, and surgical control should be attempted when feasible. Treatment interruption at pregnancy confirmation has also proven to be safe, as drugs are not formally allowed to be used during pregnancy. Drug exposure (somatostatin analogs) during early or whole pregnancy might increase the chance of a lower birth weight. Aggressive disease is uncommon and may urge individual decisions such as surgery or drug treatment during pregnancy or lactation.

Immunological screening and characterization of highly specific monoclonal antibodies against 20 kDa hGH

Background: hGH has been widely abused as a doping agent in sports for many years. There are some important approaches for the detection of hGH doping, and the ratio of 22:20 kDa GH was considered one of the most suitable detection indicators of GH abuse. Currently, effective anti-GH antibodies and related reagents are needed to develop a detection method, in particular, highly specific anti-20 kDa hGH monoclonal antibodies are a prerequisite. Herein we constructed the expression vector of 20 kDa hGH and prepared the corresponding antibodies by the immunization of the recombinant human 20 kDa into mice. Positive clones that can specifically recognize 20 kDa hGH were screened and characterized by enzyme immunoassay, Dot-ELISA and surface plasmon resonance. In total, 14 specific monoclonal cell lines were screened out. Results: By a series of characterization, it was found that the 6C8, 44H3, 12G7 and 33Y19 clones were showing much higher specificity and affinity to 20 kDa hGH, and P3H9 could recognize both 20 and 22 kDa hGH isoforms. 6C8 and 44H3 matched well with P3H9 in the surface plasmon resonance testing. The 12G7 clone had the best surface properties with an association constant of 3.4 × 109 M-1 and a dissociation constant of 2.95 × 1010 M. Conclusion: Highly specific monoclonal antibodies against 20 kDa hGH were generated, and also two paired antibodies (P3H9 and 6C8 or P3H9 and 44H3) were characterized, which can serve as the potential components for 22:20 kDa detection kit.

Growth hormone doping in sports: a critical review of use and detection strategies

GH is believed to be widely employed in sports as a performance-enhancing substance. Its use in athletic competition is banned by the World Anti-Doping Agency, and athletes are required to submit to testing for GH exposure. Detection of GH doping is challenging for several reasons including identity/similarity of exogenous to endogenous GH, short half-life, complex and fluctuating secretory dynamics of GH, and a very low urinary excretion rate. The detection test currently in use (GH isoform test) exploits the difference between recombinant GH (pure 22K-GH) and the heterogeneous nature of endogenous GH (several isoforms). Its main limitation is the short window of opportunity for detection (~12-24 h after the last GH dose). A second test to be implemented soon (the biomarker test) is based on stimulation of IGF-I and collagen III synthesis by GH. It has a longer window of opportunity (1-2 wk) but is less specific and presents a variety of technical challenges. GH doping in a larger sense also includes doping with GH secretagogues and IGF-I and its analogs. The scientific evidence for the ergogenicity of GH is weak, a fact that is not widely appreciated in athletic circles or by the general public. Also insufficiently appreciated is the risk of serious health consequences associated with high-dose, prolonged GH use. This review discusses the GH biology relevant to GH doping; the virtues and limitations of detection tests in blood, urine, and saliva; secretagogue efficacy; IGF-I doping; and information about the effectiveness of GH as a performance-enhancing agent.