Final answer:
Growth hormone stimulates protein synthesis, increases muscle mass, and decreases insulin sensitivity through direct and indirect effects on tissues. The one option that is not an effect of GH in adults is an increase in height, which does not occur post-adolescence, even with excessive levels of GH. Option 4 is the correct answer.
Step-by-step explanation:
The question pertains to the effects of growth hormone (GH) on the human body. Growth hormone, produced by the anterior portion of the pituitary gland, has several direct and indirect actions. One of the primary effects of GH is the acceleration of protein synthesis in skeletal muscle and bones, which occurs both directly and indirectly through the stimulation of insulin-like growth factor 1 (IGF-1). IGF-1, in turn, prompts the formation of new proteins in muscle cells and bone.
Growth hormone also influences body composition by promoting lipolysis, leading to the use of fatty acids as an energy source and sparing glucose. However, this process can result in decreased insulin sensitivity or a diabetogenic effect, which is characterized by higher blood glucose levels resembling those seen in diabetes mellitus. GH additionally raises blood glucose by stimulating the liver to convert glycogen into glucose.
Considering the above effects of growth hormone, the option that is not an effect of GH is increased height in adults, as excessive GH after the normal growth periods can lead to acromegaly, characterized by the enlargement of bones in the hands, feet, and face, but not a further increase in height.