Vertebrate and Plant Hormones: Types, Functions, and Regulatory Mechanisms

Hormone

A signaling molecule produced by glands that regulates physiological processes.

Peptides/proteins

A class of vertebrate hormones that includes releasing hormones, oxytocin, vasopressin, growth hormone, TSH, calcitonin, parathyroid hormone, insulin, and glucagon.

Amino acid derivatives

A class of vertebrate hormones that includes epinephrine and thyroid hormones (T3/T4).

Steroids

A class of lipid-soluble hormones that includes testosterone, estrogens, progesterone, cortisol, and aldosterone.

Lipid-soluble hormones

Hormones that can pass through cell membranes and typically include steroid hormones.

Water-soluble hormones

Hormones that cannot pass through cell membranes and include peptides and amino acid derivatives.

Releasing hormones

Hormones produced by the hypothalamus that stimulate the anterior pituitary to release other hormones.

Oxytocin

A hormone that regulates social bonding, sexual reproduction, and during and after childbirth.

Vasopressin

Also known as antidiuretic hormone (ADH), it regulates water retention in the kidneys.

Growth hormone

A hormone that stimulates growth, cell reproduction, and regeneration in humans and other animals.

Thyroid hormones

Hormones produced by the thyroid gland that regulate metabolism, including T3 and T4.

Ca2+ homeostasis

The regulation of calcium ion concentration in the body, involving hormones like calcitonin and parathyroid hormone.

Blood glucose homeostasis

The regulation of blood sugar levels, primarily involving insulin and glucagon.

Adrenal gland hormones

Hormones released by the adrenal gland, including cortisol, epinephrine, and aldosterone, which regulate metabolism, stress response, and blood pressure.

Auxins

Plant hormones that regulate growth and development.

Ethylene

A plant hormone that regulates fruit ripening and other growth processes.

Abscisic acid

A plant hormone that regulates stomatal closure and responses to stress.

Peptide hormones

Transcribed, translated, and stored in vesicles until release is needed.

Membrane receptors

Activated by water-soluble hormones and typically activate signal transduction cascades.

Steroid hormones

Synthesized via cholesterol on-demand and diffuse through membrane.

Intracellular receptors

Activated by lipid-soluble hormones and typically regulate gene expression.

Endocrine glands

Many hormones are released by discrete endocrine glands that require plentiful blood supply.

Other organs

Also release hormones, examples include stomach, small intestine, heart, and kidneys.

Hypothalamus and pituitary gland

Coordinate the release of many hormones.

Anterior pituitary

Forms from epithelial tissue and is connected to hypothalamus via capillaries.

Posterior pituitary

Forms from nervous tissue and is connected to hypothalamus via neurons.

Neuroendocrine reflex

Regulates uterine contractions as an example of positive feedback.

Anterior pituitary hormones

Often act as tropic hormones, triggering release of a third hormone.

Growth hormone releasing hormone (GHRH)

Triggers release of growth hormone from anterior pituitary.

Thyrotropin releasing hormone (TRH)

Triggers release of TSH from anterior pituitary.

Blood calcium homeostasis

Requires hormones from the thyroid gland and parathyroid glands.

Parathyroid hormone

From parathyroid gland, increases blood Ca2+ levels.

Calcitonin

From thyroid, lowers blood Ca2+ levels.

Blood glucose regulation

Requires two hormones from the pancreas: glucagon and insulin.

Glucagon

Released by α cells to increase blood glucose.

Insulin

Released by β cells to lower blood glucose.

Insulin release trigger

Triggered by excess ATP in β cells.

Glucagon mechanism

Increases glucose availability through GPCRs.

Phytoestrogens

Act as estrogen receptor agonists or antagonists, hypothesized to reduce fertility of female herbivores.