The Effect of Vitamin C on Growth Hormone Secretion

Study Overview
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Brief Summary
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Obesity is associated with reduced growth hormone (GH) secretion. GH secretion is regulated by nutritional stimuli including fasting, insulin, glucose and free fatty acids. However, the role of micronutrients, such as vitamins, on GH secretion has not been investigated in much detail. Vitamin C levels are also reduced in obesity, and the investigators recently demonstrated a possible role for dietary vitamin C intake in the regulation of GH secretion in two preliminary retrospective studies. The investigators therefore propose a more detailed prospective physiological study to examine the effects of increasing dietary vitamin C intake on GH secretion in a physiologic, intervention study. The investigators hypothesize that increasing vitamin C concentrations in obese subjects with sub-optimal plasma vitamin C levels and reduced GH secretion will increase GH secretion.

Official Title
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The Effect of Vitamin C on Growth Hormone Secretion

Conditions
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Obese, Disorder of Vitamin C, Growth Hormone Secretion Abnormality

Intervention / Treatment
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* Dietary Supplement: Placebo
* Dietary Supplement: Vitamin C 250 mg once daily
* Dietary Supplement: Vitamin C 1,000 mg once daily


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men and women age 18-60 BMI ≥ 30 kg/m2 Waist circumference ≥ 102 cm in men and ≥ 88 cm in women Plasma vitamin C concentration ≤ 23 µmol/l Peak stimulated GH ≤ 4.2 µg/l upon GHRH-arginine stimulation test Exclusion Criteria: History of hypopituitarism, pituitary surgery, pituitary/brain radiation, recent traumatic brain injury or any other condition known to affect the GH axis. History of severe chronic illness including anemia, chronic kidney disease, liver disease, oxygen dependent COPD or HIV Subjects on testosterone, glucocorticoids, anabolic steroids, GHRH, GH or IGF-1 within 3 months of enrollment Use of dietary supplements including vitamin C or once daily multi-vitamins Subjects with Hgb < 912 g/dL, SGOT > 2.5x upper limit of normal or Creatinine > 1.5 mg/dL Subjects with poorly controlled diabetes, defined as HbA1c > 8%. Changes in lipid lowering or anti-hypertensive regimen within 3months of screening Subject is currently enrolled in another investigational device or drug trial(s), or subject has received other investigational agent(s) within 28 days of baseline visit Any condition judged by the patient's physician to cause this clinical trial to be detrimental to the patient.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Vitamin C low dose<br>vitamin C 250 mg oral once daily | Dietary Supplement: Vitamin C 250 mg once daily<br> <br> |
| Active Comparator: Vitamin C high dose<br>vitamin C 1,000 mg oral once daily | Dietary Supplement: Vitamin C 1,000 mg once daily<br> <br> |
| Placebo Comparator: Placebo<br>Placebo oral once daily | Dietary Supplement: Placebo<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from Baseline in GH secretion at 4 weeks | GH secretion will be assessed by overnight frequent blood sampling to assess maximum GH, nadir GH, mean overnight GH, as well as parameters of pulsatile secretion. | Change from Baseline to 4 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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low vitamin c, reduced growth hormone secretion