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I will try to to answer you queries one by one.

What is the effect of glucagon?
Glucagon is a hormone released by alpha cells in the pancreas (Insulin is produced by beta cells). Glucagon functions exactly opposite to Insulin. Glucagon acts on liver leading to more production of glucose. In conditions such as Diabetes, its action is unchecked leading to excess levels of sugars in blood.

Does it make glucogenesis happen and helps the liver synthesize urea?
Glucagon stimulates glycogenolysis ( breakdown of glycogen) and gluconeogenesis ( formation of glucose using different things like fatty acids, amino acids etc) by the liver and kidneys. This leads to rise in blood glucose levels.

Is it true that human growth hormone stimulates triglyceride lipolysis in fat cells, milk synthesis by lactating mammary glands, and menarche, but does not produce insulin resistance?
Growth hormone induces protein synthesis and nitrogen retention and impairs glucose tolerance by antagonizing insulin action (so it indirectly produces insulin resistance). Growth hormone also stimulates lipolysis in fat cells. Milk synthesis and menarche are not directly related to growth hormone but could be co-associated with changes in other endocrine hormones along with growth hormones.

Hope I have answered your queries.

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