Endocrine Systems and Hormones

Endocrine System

A system of organs that secretes hormones into the blood.

Hormone

A chemical secreted into the blood that helps communicate a signal from one organ or organ system to another.

Water-soluble Hormones

Easily transported in the blood, these hormones are proteins that act on receptors found on the cell membrane.

Lipid-soluble Hormones

Hormones that require a protein carrier for transportation in the blood, derived from cholesterol, that act in the nucleus.

Hypothalamus-Pituitary Axis

The interaction between the hypothalamus and the pituitary gland, which regulates hormone secretion.

Anterior Pituitary

Secretes hormones including FSH, LH, ACTH, TSH, Prolactin, and Growth Hormone, influenced by hypothalamic hormones.

Posterior Pituitary

Secretes hormones such as Vasopressin (ADH) and Oxytocin, influenced by neural stimuli from the hypothalamus.

Negative Feedback

A regulatory mechanism where increased levels of hormones inhibit further secretion from the hypothalamus and pituitary.

Thyroid Hormones T3 and T4

Hormones that regulate basal metabolic rate, body temperature, and promote growth.

ACTH (Adrenocorticotropic Hormone)

Stimulates the adrenal cortex to secrete cortisol, which plays a role in stress response.

Cortisol

A fat-soluble hormone produced by the adrenal cortex, involved in immune response and metabolism regulation.

Growth Hormone (GH)

Stimulates growth and metabolism by acting on the liver and muscles to produce Insulin-like Growth Factor (IGF).

Prolactin