Adolescent Medicine · Supplementary · from Adolescent Medicine
Case 1: Adolescent Type 1 Diabetes Management
Patient Presentation
Demographics: 15-year-old female high school sophomore, competitive swimmer
Chief Complaint: "I've been losing weight even though I'm eating more, and I'm always thirsty and going to the bathroom all the time."
History of Present Illness: The patient presents to the adolescent medicine clinic with her mother with a four-week history of progressive polyuria, polydipsia, and unintentional weight loss of approximately 5 kg (11 lbs). She reports drinking up to 4 liters of water per day and waking 3-4 times nightly to urinate, which has begun affecting her school performance and swim practice. She describes persistent fatigue that has worsened over the past two weeks, causing her to miss several swim practices — something very unusual for this previously highly motivated athlete.
Her mother noticed that her daughter appeared thinner and more fatigued than usual. The patient also reports intermittent blurred vision for the past week, mild nausea without vomiting, and one episode of a vaginal yeast infection two weeks ago (treated with over-the-counter antifungal). She denies abdominal pain, fever, cough, recent illnesses, or any substance use. She denies any intentional caloric restriction or excessive exercise beyond her swim training.
The patient is concerned that her declining performance in the pool and academic difficulties will jeopardize her chances for a college swimming scholarship. She reports feeling "frustrated and scared" about her symptoms.
Past Medical History:
- No prior chronic illnesses
- Full immunization schedule up to date
- Menarche at age 12; regular menstrual periods until 2 months ago (has missed last 2 cycles)
- No prior hospitalizations or surgeries
- No known drug allergies
Medications:
- None (other than recent OTC miconazole for yeast infection)
Social History:
- 10th grade student, honor roll (grades declining over the past month)
- Competitive swimmer since age 8; practices 6 days per week, 2 hours daily
- Lives with both parents and a 12-year-old brother
- Denies tobacco, alcohol, drug use, or sexual activity (HEADSS assessment completed)
- No recent travel
- Good peer relationships; reports no bullying
- Screen time approximately 2 hours daily on weekdays
Family History:
- Mother: Hashimoto's thyroiditis (on levothyroxine)
- Maternal grandmother: type 1 diabetes (diagnosed at age 22)
- Father: healthy
- Paternal grandfather: type 2 diabetes
- Brother: healthy, no autoimmune conditions
Physical Examination
- Vital Signs: BP 108/68 mmHg, HR 94 bpm (mild tachycardia), RR 18/min, Temp 36.7°C, Weight 52 kg (down from 57 kg at last sports physical 3 months ago), Height 165 cm, BMI 19.1 kg/m² (decreased from 20.9)
- General: Alert, cooperative adolescent female; appears thin and mildly dehydrated; no acute distress; Tanner stage IV
- HEENT: Dry mucous membranes; no thyromegaly; no oral thrush; slight fruity odor to breath
- Cardiovascular: Tachycardic, regular rhythm, no murmurs; capillary refill 2.5 seconds
- Respiratory: Clear to auscultation bilaterally; no Kussmaul breathing
- Abdomen: Soft, non-tender, non-distended; no hepatosplenomegaly
- Skin: Dry skin with reduced turgor; no acanthosis nigricans; no lipodystrophy; no rashes
- Neurological: Alert and oriented x 3; cranial nerves intact; normal reflexes; no peripheral neuropathy
- Musculoskeletal: Normal muscle bulk for an athlete; no joint swelling
- Psychological assessment: PHQ-A score 8 (mild depression); reports sadness about physical changes and performance decline; denies suicidal ideation
Workup and Results
Laboratory Studies:
| Test | Result | Reference Range |
|---|---|---|
| Random plasma glucose | 382 mg/dL | 70-140 mg/dL |
| HbA1c | 11.2% | <5.7% (normal); >6.5% (diabetes) |
| C-peptide (fasting) | 0.18 ng/mL | 0.8-3.1 ng/mL (low, indicating insulin deficiency) |
| GAD65 antibodies | >250 IU/mL (positive) | <5 IU/mL |
| IA-2 antibodies | 128 IU/mL (positive) | <7.5 IU/mL |
| Zinc transporter 8 (ZnT8) antibodies | Positive | Negative |
| Insulin autoantibodies (IAA) | Positive | Negative |
| Blood pH (venous) | 7.31 | 7.35-7.45 |
| Serum bicarbonate | 18 mEq/L | 22-28 mEq/L |
| Urine ketones | Large (3+) | Negative |
| Beta-hydroxybutyrate | 3.8 mmol/L | <0.6 mmol/L |
| Serum sodium | 133 mEq/L | 136-145 mEq/L (corrected Na: 137) |
| Serum potassium | 4.8 mEq/L | 3.5-5.0 mEq/L |
| BUN | 22 mg/dL | 7-20 mg/dL (mild dehydration) |
| Creatinine | 0.8 mg/dL | 0.5-1.0 mg/dL |
| TSH | 3.2 mIU/L | 0.5-4.5 mIU/L |
| Free T4 | 1.1 ng/dL | 0.8-1.8 ng/dL |
| Anti-TPO antibodies | 48 IU/mL (mildly elevated) | <35 IU/mL |
| Celiac panel (tTG-IgA) | 8 U/mL (negative) | <20 U/mL |
| Total IgA | 180 mg/dL | 70-400 mg/dL (rules out IgA deficiency) |
| Lipid panel | Total cholesterol 198, LDL 122, HDL 48, TG 140 | Dyslipidemia common in uncontrolled T1D |
Imaging/Additional Studies:
- Point-of-care glucose confirmation: 378 mg/dL (consistent with laboratory value)
- Urinalysis: Glucosuria (4+), ketonuria (3+), pH 5.0, no leukocytes
- ECG: Sinus tachycardia at 94 bpm, normal axis, no peaked T-waves (potassium within normal range)
Clinical Image
Educational diagram illustrating the autoimmune pathophysiology of Type 1 diabetes mellitus, showing immune-mediated beta cell destruction, relevant autoantibodies, and the clinical consequences of insulin deficiency. Source: Educational illustration.
Diagnosis
New-Onset Type 1 Diabetes Mellitus with Mild Diabetic Ketoacidosis (DKA)
Key Diagnostic Criteria:
- Classic symptoms: polyuria, polydipsia, unintentional weight loss, fatigue
- Random plasma glucose >200 mg/dL (382 mg/dL) with symptoms — diagnostic of diabetes
- HbA1c 11.2% — confirms chronic hyperglycemia over the preceding 2-3 months
- Low C-peptide (0.18 ng/mL) — confirms endogenous insulin deficiency
- Multiple positive autoantibodies (GAD65, IA-2, ZnT8, IAA) — confirms autoimmune etiology (Type 1)
- Mild DKA: pH 7.31, bicarbonate 18, elevated beta-hydroxybutyrate, ketonuria
- Family history of autoimmune disease (maternal Hashimoto's, maternal grandmother T1D)
- Elevated anti-TPO antibodies indicating risk of future thyroid autoimmunity (autoimmune polyendocrine syndrome screening)
Treatment Plan
- Acute management of mild DKA:
- IV normal saline bolus 10 mL/kg over 1 hour, then maintenance fluids
- Start IV insulin infusion at 0.05-0.1 units/kg/hour (no bolus needed for mild DKA)
- Monitor blood glucose hourly; add dextrose to IV fluids when glucose falls below 250 mg/dL
- Monitor electrolytes every 2 hours; supplement potassium as needed
- Transition to subcutaneous insulin once DKA resolved (pH >7.3, bicarbonate >15, tolerating oral intake, anion gap closed)
- Initiation of basal-bolus insulin regimen:
- Basal insulin: Glargine (Lantus) 0.3-0.4 units/kg/day (starting dose ~18 units at bedtime)
- Bolus insulin: Lispro (Humalog) with meals using insulin-to-carbohydrate ratio of 1:15 and correction factor of 1:50 (starting estimates; will be refined)
- Alternative: Insulin pump therapy to be discussed after initial stabilization and education (may benefit her athletic schedule)
- Diabetes education program (multidisciplinary, over the first 2 weeks):
- Blood glucose monitoring: minimum 4 times daily (before meals and bedtime); discuss continuous glucose monitoring (CGM) with Dexcom G7 or Libre 3
- Carbohydrate counting education with a registered dietitian
- Insulin injection technique training (rotation of injection sites)
- Hypoglycemia recognition and treatment (Rule of 15: 15 g fast-acting carbohydrate, recheck in 15 minutes)
- Glucagon emergency kit training for parents
- Sick-day management rules
- Exercise management: reducing bolus insulin by 25-50% before swimming; carrying glucose tablets to practice
- Psychosocial support:
- Psychology referral for adjustment to chronic illness diagnosis in an adolescent
- Screen for diabetes distress at each visit
- Connect with peer support (diabetes camp, online adolescent T1D communities)
- School 504 plan to accommodate blood glucose monitoring, snacks, and bathroom access
- Screening for associated autoimmune conditions:
- Thyroid function monitoring annually (given elevated anti-TPO)
- Celiac screening annually for the first 4 years, then as clinically indicated
- Adrenal insufficiency screening if symptoms develop
- Follow-up schedule:
- Endocrinology within 1 week of discharge
- Telephone/telehealth check-in within 48-72 hours for insulin dose adjustments
- HbA1c every 3 months; target <7.0% (with individualization to avoid hypoglycemia)
- Annual dilated eye examination beginning 5 years after diagnosis (or at age 11, whichever is later)
- Annual urine microalbumin screening beginning 5 years after diagnosis
Key Learning Points
- Type 1 diabetes can present at any age but has a bimodal peak in childhood (ages 4-6 and 10-14); adolescent presentations may be initially missed or attributed to stress, growth spurts, or eating disorders.
- Multiple autoantibody testing (GAD65, IA-2, ZnT8, IAA) increases diagnostic sensitivity for autoimmune T1D to >95%; a low C-peptide level confirms endogenous insulin deficiency and distinguishes T1D from T2D.
- Adolescents with new-onset T1D are at high risk for associated autoimmune conditions, particularly thyroid disease (up to 30% prevalence) and celiac disease (5-8%); systematic screening is essential.
- Exercise management is one of the most challenging aspects of T1D in athletic adolescents; swimming poses unique challenges as the pump must be disconnected, and hypoglycemia risk is increased by the exercise-induced improvement in insulin sensitivity.
- The psychosocial impact of T1D diagnosis in adolescence is significant; adherence challenges peak during adolescence due to developmental needs for autonomy, peer belonging, and identity formation. A multidisciplinary approach including psychology support improves outcomes.