This randomized, active-controlled, parallel-arm, single-blind trial is to compare the effects of Dopamine agonists (DA) therapy targeting different established treatment strategies on glucose metabolism assessed by an oral glucose tolerance test.
Prolactinomas are the most common pituitary tumors, leading to hyperprolactinemia, which causes hypogonadism, infertility, and is associated with adverse metabolic effects such as insulin resistance, dyslipidemia, and obesity. Dopamine agonists (DAs), especially cabergoline, are the first-line treatment. They reduce prolactin levels and tumor size effectively. Despite their widespread use, there are no evidence-based guidelines regarding target prolactin levels during DA therapy. Limited evidence suggests that different prolactin levels may have different effects on metabolic health. This trial aims to assess glucose tolerance, insulin sensitivity, and beta-cell function-using OGTT with insulin levels-after 12 months of DA treatment, to target treatment options. In Switzerland, cabergoline is the preferred DAs for treating hyperprolactinemia. Cabergoline is available in tablet form, with doses of 0.5 mg per tablet. The standard dosing for hyperprolactinemia typically starts at 0.25 mg to 0.5 mg per week, which can be gradually increased based on the patient's response, with a usual range of 0.25 mg to 2 mg per week.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
60
Cabergoline is available in tablet form, with doses of 0.5 mg per tablet. The standard dosing for hyperprolactinemia typically starts at 0.25 mg to 0.5 mg per week, which can be gradually increased based on the patient's response, with a usual range of 0.25 mg to 2 mg per week. The dose required to achieve the target prolactin levels (pre- defined for each intervention arm) may vary between patients, so a fixed dose is not specified. This allows for individualized treatment based on each patient's response.
University Hospital Basel, Dept. of Endocrinology, Metabolism & Diabetes
Basel, Switzerland
RECRUITING2-hour post-oral glucose tolerance test (OGTT) plasma glucose levels
The OGTT is a test used to assess the ability to process glucose. It involves fasting overnight and then drinking a solution containing a measured amount of glucose (75g). Blood Samples are taken at 120 min after glucose intake.
Time frame: assessed at 12 months after randomisation
Change in Insulin sensitivity by MATSUDA Index
The Matsuda Index is a measure used to assess insulin sensitivity from the data obtained during an OGTT. The Index is derived from OGTT data and reflects whole-body insulin sensitivity by incorporating both fasting and postprandial glucose and insulin levels. The formula uses (1) fasting glucose and insulin before the glucose load and (2) mean glucose and mean insulin.
Time frame: measured at time points (0, 30, 60, 90, and 120 minutes) during the OGTT
Change in Insulin Sensitivity Index (ISI)
ISI is an OGTT-based measure that quantifies insulin sensitivity using fasting and post-load insulin and glucose values. It is similar to the Matsuda Index but has variations depending on specific formulas. Higher ISI values reflect better insulin action.
Time frame: measured at time points (0, 30, 60, 90, and 120 minutes) during the OGTT
Change in Quantitative Insulin Sensitivity Check Index (QUICKI)
QUICKI is a simple, fasting- based index to estimate insulin sensitivity, calculated as 1 / (log(Fasting Insulin) + log(Fasting Glucose)). Higher values indicate greater insulin sensitivity.
Time frame: measured at time points Screening, Month 6, Month 12, Month 24
Change in Glycated Haemoglobin (HbA1c)
HbA1c reflects average blood glucose levels over the past 2-3 months by measuring glucose-bound haemoglobin. It is used for diagnosing and monitoring diabetes, with values ≥6.5% indicating diabetes.
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Time frame: measured at time points Screening, Month 3, Month 6, Month 12
Change in Fasting glucose (mmol/L)
Fasting glucose measures baseline blood sugar levels after at least 8 hours of fasting. It is a primary diagnostic criterion for diabetes, with ≥7.0 mmol/L indicating diabetes.
Time frame: measured at time points Screening, Month 3, Month 6, Month 12
Change in Fasting insulin (µU/mL)
Fasting insulin provides insight into pancreatic insulin secretion and insulin resistance. Elevated levels often indicate insulin resistance, while low levels may suggest beta-cell dysfunction.
Time frame: measured at time points Screening, Month 3, Month 6, Month 12
Change in C-peptide (nmol/l)
C-peptide is released in equal amounts to insulin and is used to assess endogenous insulin production
Time frame: measured at time points Screening, Month 3, Month 6, Month 12
Change in Disposition Index (DI)
The DI integrates beta-cell function and insulin sensitivity, calculated as insulin secretion × insulin sensitivity. It reflects how well beta-cells compensate for insulin resistance, with lower values indicating a higher risk of diabetes.
Time frame: measured at time points Screening, Month 3, Month 6, Month 12
Change in plasma prolactin levels (ng/mL)
Change in plasma prolactin levels (ng/mL)
Time frame: measured at time points Screening, Month 3, Month 6, Month 12