Endocrine System Patho

Endocrine System

the group of tissues that secrete hormones as a means of regulating and integrating body functions

Hormones

substances produced by an organism that are transported in body fluids to stimulate specific tissues or cells into action

Amino Acids

Act fast + respond to stress

Ex: Dopamine, epinephrine, norepinephrine, thyroid hormone

Peptides, Proteins, Glycoproteins

Water- soluble, cannot enter cells, respond on surface receptors

Ex: thyroid releasing hormone, corticotropin-releasing hormone

Steroids

fat soluble, enter nucleus + change gene expression, act slower but longer

Ex: aldosterone, estrogens, testosterone, glucocorticoids

Features common to all hormones (ACT)

1. ACT on targets to produce an effect

2. Can only act on targets that express their RECEPTOR

3. Hormone synthesis and release is under strict CONTROL (negative feedback loop)

Hormonal actions

Based on the relationship between where the hormone is produced and where the biologic effects occur

Autocrine signaling

Within cells

Ex: insulin

Paracrine signaling

Between local cells

Ex: histamine

Endocrine signaling

Between cells remotely

Ex: ASH

Synaptic signaling

Within a neuron traveling to another neuron

Ex: endorphins

Neuroendocrin signaling

Within a neuron traveling through circulation to a target cell

Ex: dopamine

Cell surface receptors

Exert their actions through cytoplasmic second messenger systems

Ex: water soluble hormones

Intracellular receptors

Modulate gene expression by binding to DNA or promotors of target genes

Ex: fat soluble

Axis

Refers to a critical pathway involving multiple components that work together to regulate various physiological processes

Negative feedback

Low hormone level turns on system

High hormone level turns off system

Ex: RAAS, HPT

Positive feedback

A rise in hormone levels stimulates production of the hormone until there’s an interruption of the cycle

Ex: childbirth

HPA Axis

Forms the structural and functional basis of the neuroendocrine system

Includes: hypothalamus, pituitary gland, adrenal gland

HPA axis function

Controls the body’s stress response and cortisol production

HPA axis steps

Hypothalamus → releases CRH
Anterior pituitary → releases ACTH
Adrenal cortex → releases cortisol

Effects: ↑ blood glucose, ↑ BP, ↑ metabolism, ↓ immune response

Negative feedback: ↑ cortisol → ↓ CRH & ↓ ACTH

RAAS sytem

Regulates BP by controlling sodium and water excretion

RAAS Steps

↓ BP / ↓ GFR → kidneys release renin
Renin → angiotensinogen → angiotensin I
ACE (lungs) → angiotensin I → angiotensin II
Angiotensin II → vasoconstriction + release aldosterone & ADH

Effects: ↑ Na⁺ reabsorption, ↑ water retention, ↓ K⁺, ↑ blood volume, ↑ BP

HPT Axis

Controls metabolism, energy, and growth

HPT Axis Steps

Hypothalamus → releases TRH
Anterior pituitary → releases TSH
Thyroid gland → releases T3 & T4

Effects: ↑ metabolism, ↑ HR, ↑ temperature, ↑ energy use

Negative feedback: ↑ T3/T4 → ↓ TRH & ↓ TSH

Wake

Low melatonin

High cortisol: draw cortisol when it’s at highest

Sleep

High melatonin

Low cortisol

Where is antidiuretic hormone produced?

hypothalamus

Where is antidiuretic hormone stored?

Posterior pituitary

Where is antidiuretic hormone released?

posterior pituitary into circulation

What is the purpose of ADH?

To increase water absorption in the kidneys by making the ducts more permeable to water

concentrates the urine, reduces urine volume

dilutes the blood and increases blood volume

Where is oxytocin produced?

hypothalamus

where is oxytocin stored?

posterior pituitary

where is oxytocin released?

posterior pituitary into circulation

Oxytocin function?

causes contraction of the uterus during labor, milk ejection in lactating women, social bonding, stress relief, emotional regulation

where is growth hormone produced?

anterior pituitary