Effect of Intranasal Insulin on LH Concentrations in Man

Studies over the last few years have clearly established that at least 25% of men with type 2 diabetes have subnormal free testosterone (T) concentrations in association with inappropriately low leutinizing hormone (LH) and FSH (follicle stimulating hormone) concentrations. These patients thus suffer from hypogonadotrophic hypogonadism (HH). Obesity and metabolic syndrome are also associated with HH. Animal studies and in vitro data have shown that insulin action and insulin responsiveness in the brain are necessary for the maintenance of the functional integrity of the hypothalamo-hypophyseal-gonadal axis. Insulin concentrations can be increased in the brain by delivering insulin intranasally with vianase device. The aim of this project is to study the effect of one dose of intranasal insulin on release of LH in obese diabetic men with HH. 15 obese men with type 2 diabetes and low free T along with normal LH concentrations will be recruited for the study. The study will be carried out at the clinical center of Texas Tech (Odessa campus). There will be two study visits, each comprising of blood tests every 15 minutes over 6 hours. 40 IU of intranasal insulin or saline will be given after a baseline period of blood sampling of 2 hours. Student's t-test will be used to compare the change in LH concentrations after intranasal saline or insulin.

Inclusion criteria

• Males age 18 to 75 years
• Obesity (BMI ≥30 kg/m2)
• Type 2 diabetes
• Hypogonadotropic hypogonadism defined as calculated free testosterone concentrations below 7 ng/dl along with normal or low LH concentrations

Exclusion criteria

• HbA1c>8.5%
• Use of preprandial insulin therapy
• Use of testosterone currently or in the past 4 months
• Use of over the counter health supplements which contain androgens
• Use of corticosteroids or narcotics in the past 3 months
• Coronary event or procedure(myocardial infarction, unstable angina, coronary artery bypass, surgery or coronary angioplasty) in the previous twelve weeks
• Type I Diabetes
• Currently suffering from foot ulcer, significant periodontal disease or any other chronic infectious or inflammatory condition
• Hepatic disease (transaminase > 3 times normal) or cirrhosis
• Renal impairment (defined as glomerular filtration rate<30)
• HIV or Hepatitis C positive status
• Any other life-threatening, non-cardiac disease
• History of untreated severe obstructive sleep apnea(defined as apnea-hypopnea index ≥30)
• currently suffering from symptomatic depression, with or without treatment
• Use of an investigational agent or therapeutic regimen within 30 days of study
• Participation in any other concurrent clinical trial
• Pituitary tumor/damage/ other trophic hormone deficiency