Oxytocin Levels in Response to Pituitary Provocation Tests in Healthy Volunteers

Background: Oxytocin, secreted into the circulation through the posterior pituitary, regulates lactation, weight, and socio-behavioral functioning. Oxytocin deficiency has been suggested in patients with hypopituitarism, however, diagnostic testing for oxytocin deficiency has not been developed. Known stimuli used in the diagnosis of pituitary deficiencies - the hypertonic saline and arginine infusion tests stimulating copeptin levels, and the oral macimorelin test stimulating growth hormone levels - have also been shown to stimulate oxytocin secretion in animal models. We hypothesized that these provocation tests would stimulate plasma oxytocin levels in humans.

Methods: Basal plasma oxytocin levels were measured for all three tests. Stimulated plasma oxytocin was measured once plasma sodium >150 mmol/l for the hypertonic saline and after 45 minutes for the arginine infusion and the oral macimorelin test, expected peak of copeptin and growth hormone levels, respectively. Primary outcome was change between basal and stimulated oxytocin levels using a paired t-test.

Results: Median (IQR) age of all participants was 24 years (22, 28), 51% were female. As expected, copeptin increased in response to hypertonic saline from 4.0 pmol/L [3.3, 6.7] to 34.2 pmol/L [23.2, 45.4] (p-value <0.001) and in response to arginine infusion from 4.6 pmol/L [3.2, 6.2] to 8.3 pmol/L [6.4, 10.8] (p-value <0.001). Growth hormone increased in response to oral macimorelin from 1.6 ng/mL [0.3, 17.2] to 106.0 ng/mL [73.3, 127.2] (p-value <0.001). Oxytocin levels increased in response to hypertonic saline infusion from 0.3 pg/mL [0.3, 0.5] to 0.6 pg/mL [0.4, 0.7] (p-value 0.007), while there was no change in response to arginine infusion (basal 0.4 pg/mL [0.4, 0.6], stimulated 0.4 pg/mL [0.3, 0.6], p-value 0.6), nor to oral macimorelin (basal 38.7 pg/mL [31.1, 66.9], stimulated 34.2 pg/mL [31.2, 48.2], p-value 0.3).

Conclusion: We found that hypertonic saline infusion results in doubling of oxytocin levels. Further research will be important to determine whether this test could be used diagnostically to identify patients with oxytocin deficiency. In contrast to animal data, arginine and macimorelin did not stimulate oxytocin.

Etiology and outcome of childhood and adolescent diabetes mellitus in North India

The etiology of childhood onset diabetes mellitus (DM) varies between regions and races, and its long-term outcome is affected by social and economic factors. There are scant data on the etiology of childhood DM and outcome of multidisciplinary team management from developing countries. We retrospectively analyzed case records of 160 predominantly middle socio-economic group patients with onset of DM < or =18 years of age for etiology and features at presentation. In addition, we prospectively studied acute and chronic complications and metabolic control in a subset of 67 patients. Type 1 DM comprised 81%, type 2 DM 8%, and fibrocalculous pancreatic DM 9% of patients. Mean HbA1c was 8.0+/-1.5%. Retinopathy was present in 22% and nephropathy in 18% of those with DM duration > or =5 years (mean age 21.2+/-6.8 years, mean duration 10.2+/-4.6 years). The frequency of ketoacidosis and severe hypoglycemia was 5.0 and 3.3 episodes per 100 patient years. Mortality was 7% over 823 person years of follow up. We conclude that fairly good metabolic control is achievable in a middle socio-economic population in India, with the assistance of a diabetes education program. The frequency of microvascular complications is comparable to that in the literature. However, mortality remains unacceptably high.