IMPAIRED GROWTH HORMONE RESPONSE TO GROWTH HORMONE RELEASING FACTOR AND INSULIN‐HYPOGLYCAEMIA IN OBESITY

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Abstract
We have previously reported an impaired growth hormone (GH) response and abnormal prolactin release to insulin‐hypoglycaemia in obesity. We suggested that obese women with an absent prolactin response to hypoglycaemia (‘non‐responders’) have a disorder of hypothalamic function. We have now investigated the GH response to i. v. growth hormone releasing factor, GHRF (1–29)NH2, in 14 obese women and nine age‐matched normal‐weight women. We found a significantly reduced GH response to GHRF in the obese women as compared with controls (mean peak · SEM: obese 8·9 · 2 mu/l, controls 28 · 2 mu/l; P >0·01). When the obese women were divided on the basis of their prolactin response to insulin‐hypoglycaemia (seven ‘non‐responders’, mean weight 102 · 5 kg; seven responders, mean weight 108·8 kg) a similar GH response to GHRF was found between the two groups but the GH response to hypoglycaemia was significantly less in the ‘non‐responder’ women (mean peak ‘non‐responders’ 10·5 · 3 mu/l, responders 27·4 mu/l; P < 0·05). We conclude that obesity may be characterized by an impaired GH response to both i. v. GHRF and insulin‐hypoglycaemia, which suggests altered hypothalamic‐pitui‐tary function. The finding that the GH response to hypoglycaemia is significantly less in the obese prolactin ‘non‐responder’ women supports the hypothesis for a hypothalamic disorder.