Safety and Efficacy of Chlorthalidone in Type 1 Diabetes

Type 1 diabetes (T1D) is associated with increased urinary calcium loss, which may contribute
to the low bone mineral density and increased fracture risk observed in patients with this
condition. Chlorthalidone is a thiazide-like diuretic that is commonly used to reduce urinary
calcium excretion in other conditions such as idiopathic hypercalciuria. Its safety and
efficacy has not been specifically tested in an adolescent type 1 diabetes population.

T1D subjects with hypercalciuria and who meet inclusion/exclusion criteria will be given
chlorthalidone daily. Blood and urine tests, blood pressure, and glycemic control will be
assessed at weekly study visits for 4 weeks.

Inclusion Criteria:

- Diagnosis of T1D

- Age 12-21 years

- Tanner Stage 2 or greater pubertal development

- Urine calcium excretion ≥ 4 mg/kg/day

- Able to swallow pills

Exclusion Criteria:

- BMI > 99th percentile for age (<18 years) or BMI >35 kg/m2 (≥ 18 years)

- Coexistent conditions that may affect calcium metabolism including:

- celiac disease

- Graves' Disease

- Addison's disease

- hypo- or hyperparathyroidism

- History of diabetes related complications including:

- neuropathy

- retinopathy

- nephropathy

- gastroparesis

- History of oral or inhaled corticosteroid use for ≥ 5 consecutive days within the past
month

- History of any diuretic use within the past month

- Laboratory abnormalities on screening bloodwork including:

- estimated glomerular filtration rate <90 mL/min per 1.73 m2 of body surface area

- serum calcium >10.5 mg/dL

- serum potassium <3.5 mmol/L

- Systolic or diastolic blood pressure <5th percentile for age and sex50 for age <18
years or systolic <90 mmHg or diastolic blood pressure <60 mmHG for age ≥18 years