A pilot study of the effects of niacin administration on free fatty acid and growth hormone concentrations in children with obesity.

CONTEXT: Children with obesity have low spontaneous growth hormone (GH) secretion. High circulating free fatty acid (FFA) concentration is believed to inhibit GH secretion in those with obesity. In adults, lipolytic inhibition with niacin lowers FFA and increases GH, but there are no prior studies in children with obesity. OBJECTIVE: The objective of the study was to determine the dose and frequency of niacin administration required to lower FFA and stimulate GH in children with obesity. DESIGN: Dose-finding study of nondiabetic children ages 6-12 years with body mass index (BMI) ≥ 95th percentile given niacin 250 mg q2h × 3 doses (n = 2), 500 mg q2h × 3 doses (n = 5) or 500 mg q1h × 4 doses (n = 5). PARTICIPANTS: Eight boys and four girls (age 9.7 ± 1.8 years; BMI 26.4 ± 3.1 kg m-2 ; BMIz 2.2 ± .25) were studied. MAIN OUTCOME: Percentage of serum FFA values that were below 0.2 mEq L-1 . GH, insulin and glucose were also measured serially. RESULTS: FFA decreased as the dose and frequency of niacin increased (p = .01). Niacin 500 mg q1h 4 doses suppressed FFA < 0.2 mEq L-1 and significantly increased GH (p = .04). Adverse effects were flushing/warmth (100%), tingling (60%) and GI complaints (20-40%). CONCLUSIONS: Niacin 500 mg q1h significantly lowered serum FFA and increased GH. These pilot data suggest that high FFA is an important suppressor of GH secretion in children with obesity.

Associations between adiposity and indicators of thyroid status in children and adolescents.

BACKGROUND: In adults, obesity is associated with abnormalities of thyroid function; there are fewer studies in paediatric cohorts. OBJECTIVES: To examine associations of weight and adiposity with indices of thyroid function and thyroid-related metabolic factors in children. DESIGN/METHODS: A sample of 1203 children without obesity (body mass index [BMI] < 95th percentile; N = 631) and with obesity (BMI ≥ 95th percentile; N = 572), age 5-18 years, had height and weight measured (to calculate BMI-Z score for age and sex) and had blood collected in the morning for thyroid-stimulating hormone (TSH), free thyroxine (FT4) and leptin. A subset (N = 829) also underwent measurement of fat mass by dual-energy X-ray absorptiometry. Analyses examined associations of TSH and FT4 with adiposity and obesity-related conditions accounting for sociodemographic factors. RESULTS: Thyroid-stimulating hormone was positively related to BMIz and fat mass (both p-values < 0.001). FT4 was negatively related to BMIz and fat mass (both p-values < 0.001). TSH was positively correlated to leptin (p = 0.001) even after accounting for fat mass. CONCLUSIONS: Paediatric obesity is associated with higher TSH and lower FT4 concentrations and with a greater prevalence of abnormally high TSH. Leptin concentrations may in part explain obesity's effects on thyroid status, perhaps through leptin's effects on TSH secretion.