05 September 2026
: Case report 
Primary Care Recognition of Rabson-Mendenhall Syndrome Despite Absence of Classical Diabetic Symptoms
Challenging differential diagnosis, Rare disease
Abdullah Al Eisa ABE 1, Atheer Humoud Aldayhani ABDEF 2*DOI: 10.12659/AJCR.953067
Am J Case Rep 2026; 27:e953067
Table 1 Salient clinical and laboratory findings.
| Laboratory parameter | Result | Relationship to reference range | Clinical significance |
|---|---|---|---|
| Serum insulin | 3522.5 μU/mL | Markedly elevated | Severe hyperinsulinemia |
| HbA1c | 8.4% | Elevated (< 5.7%) | Chronic hyperglycemia |
| C-peptide | 1.01 ng/mL | Within laboratory reference range | Preserved endogenous insulin secretion |
| Testosterone | 7.18 nmol/L | Elevated for age/sex | Hyperandrogenism |
| DHEAS | 1.79 μmol/L | Mildly elevated | Androgen excess |
| Estradiol | 181 pmol/L | Interpreted in clinical context | Endocrine involvement |
| IGF-1 | 55.4 ng/mL | Low | Growth-axis disturbance |
| IGF-BP3 | 1.120 g/L | Low | Reduced IGF signaling |
| Vitamin D (25-OH) | 18 ng/mL | Low | Vitamin D deficiency |
| Pelvic ultrasound | PCOM + renal abnormalities | — | PCOM + renal abnormalities |
| Whole-exome sequencing | Insulin receptor gene mutation c.433C>T (p.Arg145Cys) | — | RMS genetically confirmed |
| DHEAS, dehydroepiandrosterone sulfate; IGF, insulin-like growth factor; IGF-BP3, Insulin-Like Growth Factor Binding Protein 3; PCOM, polycystic ovarian morphology; RMS, Rabson-Mendenhall syndrome. | |||