Lack of seasonal influence on growth hormone therapy

Variation in linear growth rates with seasonal changes has been attributed to physical activity, sunlight exposure or hormonal influences. We compared the growth hormone (hGH) induced growth rates in 15 hypopituitary children aged 2 to 17 years during two 4-month periods. Subjects did not receive hGH 4 months before the treatment periods. With subjects receiving hGH, comparison of the growth rates during spring-summer (April-August) and fall-winter (October-February) did not differ significantly (8.25 +/- 2.02 vs 8.75 +/- 1.77 cm/yr). Similarly, when growth during these same periods was compared for all subjects while off of hGH therapy, the growth rates were not significantly different in the spring-summer period (3.04 +/- 1.80) than fall-winter period (2.62 +/- 2.97). Rates of growth during therapy exceeded those during periods without therapy (p less than 0.005). These observations indicate that growth rate during therapy with hGH is not influenced by seasonal factors.