Case presentation

Patient presentation and history

A 26-year-old Vietnamese man presented to the emergency department of Sana Klinikum Lichtenberg in December 2022, following a work-related accident. The patient reported acute pain in the left lower leg. Due to language barriers (the patient spoke only Vietnamese), all communication was facilitated through Triaphon, a phone-based translation service (Triaphon GmbH, Berlin, Germany).

Physical examination revealed a patient of relatively small stature, 1.70 m tall and weighing 59 kg, corresponding to a BMI of 20.4 kg/m², consistent with a normal weight range without overt signs of malnutrition or obesity. Focused musculoskeletal examination of the left lower extremity demonstrated pain, swelling, and deformity consistent with a tibial shaft fracture. Notably, general physical examination revealed striking findings: complete absence of secondary pubic hair and prepubertal-appearing external genitalia with small testicular volume, features highly suggestive of hypogonadotropic hypogonadism [2]. Pubertal development was not formally staged using the Tanner scale at the time of presentation; however, clinical examination revealed prepubertal external genitalia, absence of pubic hair, and qualitatively small testicular volume, consistent with Tanner stage G1P1 [4].

The patient's medical history was unremarkable, with no reported chronic conditions or regular medications. However, a significant historical detail emerged: the patient had contracted mumps at age 10. This raised clinical concern for possible post-infectious orchitis, which could have contributed to testicular dysfunction, although primary hypogonadism caused by orchitis would typically present with elevated gonadotropins rather than the low levels subsequently observed.

Radiographic findings

Standard anteroposterior and lateral radiographs of the left lower leg revealed a spiral fracture of the tibial shaft. Computed tomography imaging was performed for surgical planning and confirmed the fracture pattern. Remarkably, both radiographic modalities clearly demonstrated unoccluded (open) growth plates at the proximal and distal tibia (Figure 1), a finding distinctly abnormal in a 26-year-old man, as physeal closure typically occurs by age 16-18 in males.

The presence of open growth plates in an adult patient immediately raised suspicion of an underlying endocrine disorder affecting skeletal maturation, prompting further investigation.

Figure 1: Preoperative radiographs of the left ankle showing a spiral fracture of the tibial shaft with persistently open growth plates (arrows indicate open physes at the proximal and distal tibia).(A) Anteroposterior long view; (B) Anteroposterior short view; (C) Lateral view

Laboratory investigations

Given the suspicious clinical and radiographic findings, comprehensive endocrine evaluation was initiated. Serum samples were collected on three consecutive days, with blood drawn at 8:45 AM each day to control for circadian variation in hormone levels. The following results were obtained:

The hormonal pattern revealed low testosterone levels accompanied by inappropriately low (rather than elevated) gonadotropin levels, confirming secondary (hypogonadotropic) hypogonadism rather than primary testicular failure. Additional pituitary function tests, including thyroid-stimulating hormone (TSH), prolactin, adrenocorticotropic hormone (ACTH), and growth hormone axes, were within normal limits, suggesting isolated gonadotropin deficiency (see Table 1). Other pituitary axes were not systematically evaluated at the time of trauma admission, and free T4, morning cortisol, and insulin-like growth factor 1 (IGF‑1) were not measured, which limits the completeness of the initial endocrine workup.

Hormone | Patient Values | Reference Range
Testosterone (ng/dL) | 15.0-20.0 | 249-836
LH (IU/L) | 0.17-0.22 | 1.70-8.60
FSH (IU/L) | 0.66-0.69 | 1.50-12.4
TSH (mIU/L) | Normal | Normal
Prolactin | Normal | Normal
ACTH | Normal | Normal

Diagnosis

Based on the constellation of clinical findings (prepubertal physical appearance, absent secondary sexual characteristics), radiographic evidence (unoccluded growth plates at age 26), and laboratory confirmation (low testosterone with low LH and FSH), the diagnosis of hypogonadotropic hypogonadism was established.

Surgical management

The acute tibial fracture required orthopedic intervention. The patient underwent closed reduction and internal fixation with an intramedullary interlocking nail under general anesthesia. The surgical procedure was performed using standard technique with fluoroscopic guidance. Proximal and distal interlocking screws were placed to provide rotational and axial stability (Figure 2). The surgical procedure proceeded without complications. Postoperative radiographs confirmed satisfactory fracture reduction and hardware positioning.

Figure 2: Postoperative radiographs of the left lower leg showing intramedullary interlocking nail fixation with satisfactory fracture alignment and hardware position.(A) Anteroposterior view; (B) Lateral view

Endocrinological management and follow-up

Following endocrinologic consultation, the patient was initiated on testosterone replacement therapy using intramuscular testosterone undecanoate 1000 mg. Injections were scheduled at baseline, after six weeks, and subsequently every 12 weeks, in line with current recommendations for long-acting testosterone formulations. This regimen was chosen because of its convenient dosing interval, reliable pharmacokinetic profile, and ability to induce stable serum testosterone levels sufficient for virilization.

The therapeutic goals were to induce the development of secondary sexual characteristics, increase muscle mass and bone mineral density, promote growth plate closure, and improve overall metabolic health and quality of life. A structured monitoring plan was established, including regular assessment of serum testosterone levels, hematocrit and hemoglobin, as well as clinical evaluation of virilization, mood, and sexual function. In addition, dual-energy X-ray absorptiometry (DEXA) was planned at baseline and at one- to two-year intervals to monitor bone mineral density. At the time of writing, no follow-up imaging or DEXA measurements are yet available; therefore, any statements regarding growth plate closure and long-term skeletal outcome remain speculative and must be interpreted with caution.