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STUDY QUESTION Can mice serve as a translational model to examine the reproductive consequences of pubertal suppression with GnRH agonist (GnRHa) followed by testosterone (T) administration, a typical therapy in peripubertal transmasculine youth? SUMMARY ANSWER An implanted depot with 3.6 mg of GnRHa followed by T enanthate at 0.45 mg weekly can be used in peripubertal female mice for investigating the impact of gender-affirming hormone therapy in transmasculine youth. WHAT IS KNOWN ALREADY There is limited knowledge available in transgender medicine to provide evidence-based fertility care, with the current guidelines being based on the assumption of fertility loss. We recently successfully developed a mouse model to investigate the reproductive consequences of T therapy given to transgender men. On the other hand, to our knowledge, there is no mouse model to assess the reproductive outcomes in peripubertal transmasculine youth. STUDY DESIGN, SIZE, DURATION A total of 80 C57BL/6N female mice were used in this study, with n = 7 mice in each experimental group. PARTICIPANTS/MATERIALS, SETTING, METHODS We first assessed the effectiveness of GnRHa in arresting pubertal development in the female mice. In this experiment, 26-day-old female mice were subcutaneously implanted with a GnRHa (3.6 mg) depot. Controls underwent a sham surgery. Animals were euthanized at 3, 9, 21 and 28 days after the day of surgery. In the second experiment, we induced a transmasculine youth mouse model. C57BL/6N female mice were subcutaneously implanted with a 3.6 mg GnRHa depot on postnatal day 26 for 21 days and this was followed by weekly injections of 0.45 mg T enanthate for 6 weeks. The control for the GnRH treatment was sham surgery and the control for T treatment was sesame oil vehicle injections. Animals were sacrificed 0.5 weeks after the last injection. The data collected included the day of the vaginal opening and first estrus, daily vaginal cytology, weekly and terminal reproductive hormones levels, body/organ weights, ovarian follicular distribution and corpora lutea (CL) counts. MAIN RESULTS AND THE ROLE OF CHANCE GnRHa implanted animals remained in persistent diestrus and had reduced levels of FSH (P  = 0.0013), LH (P  = 0.0082) and estradiol (P  = 0.0155), decreased uterine (P  < 0.0001) and ovarian weights (P  = 0.0002), and a lack of CL at 21 days after GnRHa implantation. T-only and GnRHa+T-treated animals were acyclic throughout the treatment period, had sustained elevated levels of T, suppressed LH levels (P  < 0.0001), and an absence of CL compared to controls (P  < 0.0001). Paired ovarian weights were reduced in the T-only and GnRHa+T groups compared with the control and GnRHa-only groups. LARGE SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION Although it is an appropriate tool to provide relevant findings, precaution is needed to extrapolate mouse model results to mirror human reproductive physiology. WIDER IMPLICATIONS OF THE FINDINGS To our knowledge, this study describes the first mouse model mimicking gender-affirming hormone therapy in peripubertal transmasculine youth. This model provides a tool for researchers studying the effects of GnRHa-T therapy on other aspects of reproduction, other organ systems and transgenerational effects. The model is supported by GnRHa suppressing puberty and maintaining acyclicity during T treatment, lower LH levels and absence of CL. The results also suggest GnRHa+T therapy in peripubertal female mice does not affect ovarian reserve, since the number of primordial follicles was not affected by treatment. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the Michigan Institute for Clinical and Health Research grants KL2 TR 002241 and UL1 TR 002240 (C.D.C.); National Institutes of Health grants F30-HD100163 and T32-HD079342 (H.M.K.); University of Michigan Office of Research funding U058227 (A.S.); American Society for Reproductive Medicine/Society for Reproductive Endocrinology and Infertility grant (M.B.M.); and National Institutes of Health R01-HD098233 (M.B.M.). The University of Virginia Center for Research in Reproduction Ligand Assay and Analysis Core Facility was supported by the Eunice Kennedy Shriver NICHD/NIH grants P50-HD028934 and R24-HD102061. The authors declare that they have no competing interests. [ABSTRACT FROM AUTHOR]

• Compared the release dynamics of three different delivery methods of subcutaneous testosterone administration. • The body's overall exposure to T seems similar across administration methods for T enanthate. • Pellets and silastic tubing allow for quick return to baseline T levels and regular estrous cyclicity. • Silastic implants can be used for long-term elevation in T levels. Transmasculine individuals are often prescribed testosterone (T) for masculinizing hormone therapy. Mouse models mimicking transmasculine T therapy require reliable long-term T administration. The objectives of this study were three-fold, namely, to compare: 1) the release dynamics of three different subcutaneous delivery systems of T enanthate administration (subcutaneous injections, commercially available pellets, and silastic implants) over a 6-week period in postpubertal C57BL/6N mice, 2) to compare the timing for T levels in plasma to return to baseline and cyclicity to resume after cessation of T between injections and pellets, 3) to utilize silastic implants to achieve sustainable increase in T levels utilizing T enanthate and crystalline T. All three modes of T administration resulted in an increase in T levels in plasma. Pharmacokinetic analyses showed a similar overall exposure to T enanthate over 6 weeks (integrated area) for, subcutaneous injection (0.45 mg two times per week and 0.90 mg one time per week), pellet (5 mg 60-day release), and silastic implant (5 mg 21 week) groups. Crystalline T had lower solubility and a decreased integrated area compared to T enanthate, even when implanted at a higher dosage, indicating different pharmacokinetic profiles based on type of T formulation when utilizing the same silastic delivery method. Surgical removal of pellets and silastic tubing led to a quick drop in T levels and resumption of estrous cyclicity, while cessation of injections required a long washout period for T levels to drop and estrous cycles to resume. Sustained elevation in T levels was achieved for at least 21 weeks with silastic implants. As all three delivery methods are able to elevate T levels in female mice for at least 6 weeks, choice of T administration method should be based on outcomes of interest and study design. [ABSTRACT FROM AUTHOR]

Many transgender youth seek gender affirming care, such as puberty suppression, to prolong decision-making and to align their physical sex characteristics with their gender identity. During peripubertal growth, connective tissues such as tendon rapidly adapt to applied mechanical loads (e.g., exercise) yet if and how tendon adaptation is influenced by sex and gender affirming hormone therapy during growth remains unknown. The goal of this study was to understand the how pubertal suppression influences the structural and functional properties of the Achilles tendon using an established mouse model of transmasculine gender affirming hormone therapy. C57BL/6N female-born mice were assigned to experimental groups to mimic gender-affirming hormone therapy in human adolescents, and treatment was initiated prior to the onset of puberty (at postnatal day 26, P26). Experimental groups included controls and mice serially treated with gonadotropin release hormone analogue (GnRHa), delayed Testosterone (T), or GnRHa followed by T. We found that puberty suppression using GnRHa, with and without T, improved the overall tendon load capacity in female-born mice. Treatment with T resulted in an increase in the maximum load that tendon can withstand before failure. Additionally, we found that GnRHa, but not T, treatment resulted in a significant increase in cell density at the Achilles enthesis., Competing Interests: DISCLOSURES The authors declare no conflict of interest.

Objective: Considering that glucose is an important component of seminal plasma and is a cryoprotectant at high concentrations, the aim of this study was to investigate the possible association of glucose levels in fresh semen with the sperm survival and motility rates following cryopreservation., Methods: This was a prospective study including 149 men undergoing semen analysis due to male and/or female infertility. The seminal samples were analyzed according to the World Health Organization standards and glucose concentrations were measured using a dipstick glucometer. Samples were cryopreserved with Test Yolk Buffer-Gentamicine freezing medium under liquid nitrogen for an average of 120 days. The frozen aliquots were thawed at 37°C for 10 minutes and analyzed using the same methods and protocols used pre-freezing., Results: Glucose levels ranged from 14 to 99 mg/dL and were similar in individuals with normal (n=100) vs. abnormal (n=49) semen analysis. The rates of sperm recovery (total, alive or motile sperm) in the cryopreserved samples did not change among samples with different glucose levels (p>0.05, Kruskal-Wallis ANOVA and Spearman's correlation coefficient)., Conclusions: There appears to be no association between glucose levels in human semen samples and their resistance to cryopreservation.

Purpose: To compare sperm recovery from slow versus rapid thawing technique using thirty-eight normozoospermic human sperm samples, as follows. Twentyone samples from men taking part in routine infertility screening exams (infertile group) and seventeen from proven fertile volunteer men with at least one child (fertile group)., Materials and Methods: After analysis of motility, concentration, strict morphology and functional integrity of membranes, sperm was divided into two aliquots of 0.5 mL each and frozen in TyB-G medium. Samples were thawed at room temperature (25 ± 2° C) for 25 minutes (slow thaw) or in a water bath at 75° C for 20 seconds followed by water bath at 37° C for 3 minutes (rapid thaw). After thawing, motility, strict morphology and functional integrity of membranes were evaluated by a blinded investigator. The results were expressed as mean ± standard deviation for parametric variables and analyzed using Student's t-test. Data with unpaired non-parametric variables were expressed as median (interquartile range) and analyzed by the Mann-Whitney test. Wilcoxon test was used to analyze non-parametric paired variables., Results: There was no significant difference between techniques for total and progressive motility, percentage of normal morphological forms, hypoosmotic swelling test., Conclusions: Although the rapid thawing protocol was completed in a shorter time (three minutes and 20 seconds versus 25 minutes, respectively), it wasn't harmful since both techniques showed comparable spermatozoa recovery. Additional research is needed to confirm its safety in clinical research before introducing this methodology in routine assisted reproduction.