Overview
Somatotropin (176-191), also known as HGH Fragment 176-191, is a synthetic peptide derived from the tail end of the human growth hormone (HGH) molecule, specifically corresponding to amino acids 176 through 191 of that larger protein. It belongs to the growth hormone peptide family and is classified as a fragment of somatotropin, the naturally occurring growth hormone produced by the pituitary gland. The peptide contains a cyclic disulfide bond between two cysteine residues, which contributes to its structural stability and distinguishes it from a simple linear chain. With a molecular weight of approximately 1799.1 Da and the molecular formula C78H123N23O22S2, it is a relatively small but structurally defined fragment that researchers have used to investigate the specific functional roles of different regions within the growth hormone molecule. Somatotropin (176-191) is available strictly for laboratory and research purposes and is not intended for human consumption or clinical use.
Research & Bioactivity
Somatotropin is a peptide hormone that has been extensively studied in the context of growth regulation, endocrine physiology, and developmental biology. Researchers have examined its role in longitudinal bone growth and skeletal maturation, including in cohort studies involving children with chromosomal differences such as 45,X/46,XY mosaicism, where growth patterns and height outcomes have been analyzed in relation to hormonal profiles. Studies have also investigated somatotropin's involvement in reproductive endocrinology, including its potential influence on ovarian function and intracellular signaling pathways relevant to follicular development in animal and in vitro models. Research has explored connections between somatotropin and lactation-related hormonal changes, with some clinical studies examining how physiological and emotional states during the perinatal period may affect postpartum hormone levels, including those associated with milk production. Additionally, somatotropin has appeared in oncology research contexts, where its interactions with growth factor signaling pathways — such as those involving hormone receptor-positive breast cancer subtypes — have drawn scientific interest due to its broader role in cellular proliferation and metabolic regulation.
Published Research
Positive emotion interventions as a non-pharmacological approach to boost colostrum secretion: a randomized controlled trial.
Ding L, He M, Zhu Y, Zhang X, Zhao Y — 2026
Pregnancy emotional states can influence postpartum colostrum delivery, and lactational capacity establishes 1-5 days postpartum. Breast milk production capacity is key to promoting breastfeeding. This study applied positive psychology interventions to late-pregnancy primiparous women, aiming to explore how emotional regulation affects postpartum lactation-related hormone changes and in-hospital breastfeeding outcomes. Participants were recruited from a gynecology and obstetrics hospital in China. Positive writing interventions were delivered via WeChat electronic questionnaires: the control group recorded "first three things" and the intervention group "three good things," twice weekly. Key outcomes (lactation hormones, neonatal milk consumption, breastfeeding outcomes) were collected, and generalized estimating equations (GEE) were used to analyze repeated-measurement data. Jan-Aug 2022, 204 (95 intervention, 109 control) were finally analyzed after excluding dropouts. GEE analysis showed the intervention group had a significantly higher resilience score than the control group (15.55 vs. 15.01; Wald χ = 4.53, P = 0.033). No significant differences were found between groups in anxiety, depression, positive affect and negative affect schedule (PANAS) scores, or breastfeeding scores. Post-delivery, prolactin (PRL) levels differed significantly between groups (P = 0.031), but insulin-like growth factor-1 (IGF-1) levels did not (P > 0.05). Breastfeeding behavior effects also showed no inter-group differences. This study shows the positive psychological intervention based on the "three good things" approach can effectively increase primiparous women's psychological resilience and promote prolactin secretion, but has no significant effect on breastfeeding behaviors. Additionally, the intervention tends to improve their postnatal positive emotions and reduce anxiety and negative emotions. This study provides clinical evidence for promoting colostrum secretion via prenatal positive psychology interventions.
Transcriptomic changes in tomato brown rugose fruit virus-infected tomato in response to low-dose gamma irradiation.
Tokhmechi K, Koolivand D, Rostami M, Hajiloo N, Ghorbani A — 2026
Tomato brown rugose fruit virus (ToBRFV) is a highly destructive and rapidly spreading tobamovirus that poses a serious threat to global tomato production. While low-dose gamma irradiation has emerged as a promising non-chemical strategy to enhance host resistance, the molecular mechanisms and transcriptomic reprogramming underlying this induced resistance remain largely unexplored. In this study, we employed a transcriptome-wide RNA sequencing approach to elucidate the specific gene expression networks and defense pathways activated in ToBRFV-infected tomato plants in response to low-dose gamma irradiation, addressing a critical gap in our understanding of host-virus interactions under irradiation priming. Naturally infected tomato seeds were exposed to an optimized gamma dose of 15 Gy, and transcriptomic profiles of irradiated plants were compared with those of non-irradiated infected controls. RNA-Seq analysis identified 469 differentially expressed genes (DEGs), including 157 upregulated and 312 downregulated transcripts (FDR < 0.05), indicating that gamma irradiation induces extensive transcriptional reprogramming. Functional enrichment analyses revealed significant activation of pathways related to metabolic reorganization, antioxidant defense, plant hormone signal transduction, secondary metabolite biosynthesis, and MAPK signaling. Notably, key defense-associated genes encoding peroxidases, protein kinases, and tetratricopeptide repeat (TPR) domain-containing proteins were strongly upregulated, suggesting enhanced reactive oxygen species (ROS) detoxification, stress signal amplification, and potential restriction of viral replication. In contrast, several growth- and development-related transcription factors and heat shock proteins were markedly downregulated, reflecting a shift in resource allocation toward defense responses. Quantitative RT-PCR validation of selected hormone-related genes confirmed the reliability of the RNA-Seq data and highlighted the coordinated involvement of auxin, ethylene, and gibberellin signaling in stress adaptation. Collectively, our results provide novel molecular evidence defining how low-dose gamma irradiation primes endogenous defense networks to reduce viral accumulation. This study offers new insights into the host-mediated transcriptional regulation of resistance against ToBRFV, establishing a foundation for future functional studies on irradiation-induced immunity.
Growth Patterns and Bone Maturation in Children with Sex Chromosomal (45,X/46,XY) DSD.
Bosmans J, Herregods N, van Gremberghe I, van den Akker E, Atapattu N, et al. — 2026
OBJECTIVE: To assess growth patterns and bone maturation in children with 45,X/46,XY mosaicism and to optimise final height prediction. DESIGN: Multicenter retrospective registry-based cohort study. METHODS: Ninety-five cases of 45X/46XY mosaicism from 26 centers were included. Longitudinal growth data were available for 54 participants and stratified by external genitalia score (EGS): Group 1 (EGS 0-4) and Group 2 (EGS 4.5-12). Growth was evaluated using mean height SDS based on male and female references. Bone age was reassessed centrally using the Greulich and Pyle method. Predicted adult height (PAH) and target height (TH) were compared with near-final height (nFH) using male and female standards. GH treatment outcomes were analyzed. RESULTS: Mean nFH was 157.5 cm in Group 1 and 160.3 cm in Group 2 (n.s.). Growth aligned more closely with female reference curves, with nFH at -0.7 SDS (Group 1) and -0.3 SDS (Group 2) on female charts, and -2.0 and -1.6 SDS on male charts. Bone age was delayed using female standards and advanced using male standards. Female-based PAH slightly underestimated nFH, whereas male-based PAH slightly overestimated it. PAH approximated nFH more accurately than TH. nFH was similar in those who did and did not receive GH treatment, although interpretation was limited by small sample size and treatment bias. CONCLUSION: Female growth charts and bone age readings best reflect longitudinal growth and maturation in individuals with 45,X/46,XY DSD and provide the most accurate prediction of nFH. Larger prospective studies are needed to guide evidence-based treatment decisions.
Can a focus on intracellular signaling assist us with ovarian stimulation in poor-prognosis patients?
Toner JP, Pirtea P, de Zieger D — 2026
Poor ovarian response remains one of the most challenging phenotypes in reproductive medicine. Research suggests that diminished ovarian reserve (DOR), advanced maternal age (AMA), and unexpected poor response (POR) may be due to different pathophysiologies, requiring distinct clinical management. This review focuses on the biological mechanisms that may provide an avenue for improved clinical outcomes by enhancing oocyte quality through more targeted therapy: 1. differing FSH isoforms, 2. FSH dose effects, 3. distinct signaling pathways of LH and hCG, 4. androgen priming, 5. growth hormone, 6. letrozole co-treatment, 7. coenzyme Q10, 8. Platelet-rich plasma and 9. mTOR inhibitors. Basic and clinical evidence is presented, and the therapeutic implications for treatment of the primary defect are explained. Although the clinical evidence is not yet strong for many of these factors, all are biologically plausible. This constitutes a "call to action" to correctly evaluate their possible role in improving ART outcomes.
Evolving Treatment Paradigms in Hormone Receptor-Positive, Human Epidermal Growth Factor 2-Negative Metastatic Breast Cancer.
Soliman S, Zitter R, Walker S, Chmura S, Eniu A, et al. — 2026
Hormone receptor-positive, human epidermal growth factor 2 (HER2)-negative metastatic breast cancer (MBC) represents the most common subtype of MBC and has undergone substantial therapeutic evolution. Treatment has shifted from sequential endocrine therapy (ET) and chemotherapy toward personalized strategies incorporating molecularly targeted agents and antibody-drug conjugates (ADCs), with increasing emphasis on quality of life and shared decision making. CDK4/6 inhibitors plus ET remain a first-line standard of care in high-resource settings, demonstrating consistently improved progression-free survival (PFS) and, for select agents, overall survival (OS). Management in special populations requires additional consideration of trial and real-world data, toxicity profiles, and patient preferences. Beyond ET, ADCs are reshaping the landscape. Trastuzumab deruxtecan expanded therapeutic utility across HER2-low and HER2-ultralow disease, whereas sacituzumab govitecan and datopotamab deruxtecan provide later-line options. As ADCs emerge as earlier therapies, questions regarding sequencing, cross-resistance, and toxicity remain central to clinical decision making. Metastasis-directed therapy (MDT) in oligometastatic and oligoprogressive breast cancer also requires nuanced decision making. Despite high local control rates with stereotactic body radiotherapy, randomized trials have not demonstrated consistent improvements in PFS or OS in unselected populations. Current evidence supports systemic therapy as the foundation of management, with MDT selectively considered for oligoprogression, symptom prevention, or within clinical trials. Ultimately, management of hormone receptor-positive/HER2-negative MBC requires dynamic integration of tumor biology, systemic therapy advances, and patient-defined goals of care. As therapeutic complexity increases, shared decision making and equitable access to evidence-based and supportive care services remain essential for delivering high-quality, individualized oncology care.