INTRODUCTION
Hello steemites, It's a great privilege to made another post here. So I will be continuing my lectures on what hormone is.Thank you.

BASED ON MECHANISMS OF ACTION
hormones can be classified into:

Hormones that bind to cell surface receptors, including:

Hormones that mediate their actions, using cAMP as second messenger, including glucagon, calcitonin and somatostatin

Hormones that mediate their actions using cGMP as second messengers, including nitric oxide and atrial natriuretic factor.

Hormones that mediate their activities using calcium or phosphatidyl-inositol or both, as second messengers including gastrin, oxytocin, angiotensin II and antidiuretic hormone.
Hormones that mediate their activities using kinase or phosphatase as second messengers including insulin, growth hormone, erythropoietin and prolactin.

HORMONES THAT BIND TO INTRACELLULAR RECEPTORS
including androgens, estrogens, progestins, calcitriol, glucocorticoids and thyroid hormones.

Based on their mode of transportation from their point of synthesis/release to their target sites or sites of action, we have:

Autocrine hormones, which bind to receptors on the surfaces of cells that released them and exert their effects on the same cells.

Paracrine hormones, which are released into the extracellular space, from where they diffuse to neighboring target sites to exert their effects

Endocrine hormones, which are released from their sites of synthesis into the general bloodstream for onward transportation to several target sites throughout the body.

HORMONAL CONTROL OF GLYCOGEN AND ADIPOSE TISSUE METABOLISM

Glycogen is the storage form of glucose, stored mainly in the liver and muscle tissues

. The hormonal response to glycogen metabolism is largely controlled by blood levels of glucose, the body’s primary metabolic fuel

Major hormones involved in the regulation of biological fuels in the body include insulin, glucagon, epinephrine and cortisol.

These hormones exert their effects at the major storage sites of glucose including the liver, muscle and adipose tissues

Glucagon, insulin and somatostatin are peptide hormones synthesized and secreted by α, β and δ cells of the pancreas, respectively.

ROLE OF GLUCAGON IN GLYCOGEN METABOLISM

After several hours of carbohydrate intake, there is reduction in blood glucose levels, which triggers secretion of glucagon from the α-cells of the pancreas, while inhibiting secretion of insulin.

In the liver, secreted glucagon functions to counter the low blood glucose levels by stimulating gluconeogenesis and glycogenolysis, while inhibiting glycogenesis and glycolysis

Glucagon also enhances mobilization and breakdown of fatty acids in adipose tissues

MECHANISM OF ACTION

Glucagon binds to its receptors (G-protein coupled receptors) and activates the enzyme, adenylate cyclase.

Activated adenylate cyclase then converts ATP to 3,5’-cyclo-AMP (cAMP), which binds to and activates the enzyme, protein kinase A(PK-A).

Activated PK-A has three potential functions:

Activated PK-A phosphorylates active glycogen synthase, converting it to the inactive glycogen synthase hence, terminating the synthesis of glycogen.

Activated PK-A also activates a second protein kinase, which in turn, phosphorylates inactive glycogen phosphorylase, converting it to the active glycogen phosphorylase

Active glycogen phosphorylase then converts glycogen to glucose-1-phosphate, which in turn, is converted to glucose-6-phosphate.

Glucose-6-phosphate is finally converted to free glucose, for maintenance of blood glucose levels.

Furthermore, activated PK-A inhibits the inactivation of glycogen phosphorylase by inhibiting the enzyme, protein phosphatase (PP).

Protein phosphatase is involved in the dephosphorylation of the phosphoproteins hence, inhibits glycogen breakdown.

By inhibiting this enzyme (PP), all phosphorylation reactions needed for glycogen breakdown are allowed to proceed and glycogen is consequently broken down to form glucose.

In contrast to the above, when intracellular level of cAMP reduces, protein phosphatase becomes active, leading to dephosphorylation of phosphoproteins in the cascade.

This in turn, inhibits glycogen breakdown and activates glycogen synthesis.

The entire process of activation and inactivation of proteins through phosphorylation and de-phosphorylation is known as inter-conversion.

Along the glycolytic pathway, glucagon also inhibits pyruvate kinase through cAMP-dependent phosphorylation.

This blocks the conversion of phosphoenol pyruvate (PEP) to pyruvate and prevents oxidation of pyruvate.

Consequent accumulation of phosphoenol pyruvate then favors gluconeogenesis, as against glycolysis.

Thanks to@kingreechy for the privilege.