GH1 and Leigh syndrome: Pathologically, an excess of serum hGH due to a hypersecreting pituitary adenoma causes acromegaly (3), while a subnormal production of pituitary hGH causes growth hormone (GH) deficiency and inactivating mutations of the growth hormone receptor (GHR) leads to the states of GHR resistance/insensitivity termed Laron syndrome (LS) (4).