Melatonin is structurally similar to corticosteroids

Melatonin is produced in the pineal gland

Melatonin's main function is to regulate functions related to light and changes in day length

Melatonin affects skin pigmentation

Secretion of molecules that diffuse locally and trigger a response on neighboring cells

Secretion of molecules that diffuse into the bloodstream and trigger a response in target cells anywhere in the body

Secretion of molecules that diffuse locally and trigger a response in the same cells that secreted them

Secretion of neurotransmitters that diffuse across synapses and trigger a response in cells of target tissues (neurons, muscles, and glands)

Calcitonin

Parathyroid hormone

Melatonin

Oxytocin

Antidiuretic hormone

Calcitonin

Parathyroid hormone (PTH)

Thyroxine

Melatonin

Triiodothyronine

Prolactin . . . anterior pituitary

Prolactin . . . posterior pituitary

Oxytocin . . . anterior pituitary

Oxytocin . . . posterior pituitary

Prolactin . . . mammary glands

Iodine

Potassium

Zinc

Copper

Epinephrine is secreted into a synapse to excite a post-synaptic neuron

Insulin is secreted by the pancreas to lower blood-glucose levels

Adrenocorticotropic hormone is secreted to stimulate secretion of cortisol

All of these are endocrine interactions

Insulin levels spike, facilitating the storage of glucose into cells

Insulin levels drop, facilitating the release of glucose from cells

Glucagon levels spike, promoting the breakdown of glycogen

Glycogenolysis begins to occur

Gluconeogenesis activity increases

They act as local regulators

Tyrosine-derivative hormones are water-soluble

Their receptors are found on the cell membrane

Binding to its receptor can initiate a signal transduction cascade

Neuroendocrine signaling

Synaptic signaling

Autocrine signaling

Paracrine signaling