Patho Exam 1: Endocrine

Parts of the central endocrine system

pineal gland

pituitary gland

hypothalamus

Dedicated function endocrine glands

only have the function of releasing and regulating hormones

Thyroid, parathyroid, adrenal glands

Mixed function endocrine glands

organs that have additional functions, and release endocrine hormones

Ex: kidneys, reproductive organs

Endocrine Gland

An organ that produces and releases chemicals either through ducts or into the bloodstream.

Hormone

Produced by glands. Released into bloodstream. Reach their target slower. Have a longer lasting effect on the body. wide dispersal.

agonist

a molecule that, by binding to a receptor site, stimulates a response

partial agonist

a drug that binds to a receptor and causes a response that is less than that caused by a full agonist

antagonist

A substance that blocks normal neurotransmitter functioning.

Endocrine cells release hormones where?

into the blood stream

How do hormones achieve different effects on various organs?

Different organs have different receptor subtypes for the same hormone.

Neurotransmitters

Produced by neuron. Released into synaptic cleft of Target site. Reach their target quickly. Have short lasting effect on the body. Precise delivery.

Neurosecretory cell

a neuron that secretes a hormone or hormonelike substance

Endogenous ligand

any substance, produced within the body, that selectively binds to the type of receptor that is under study

Three basic responses a hormone has once binding to a receptor

1. Alters channel permeability by acting on pre-existing channel-forming proteins

2. Acts through second-messenger system to alter activity of pre-existing proteins

3. Activates specific genes to cause formation of new proteins

Three Types of Hormones:

Peptide and Protein hormones

Amino Acid Derived hormones

Steroids Hormones

peptide and protein hormones are made of:

chains of amino acids

amino acid hormones

hormones composed of proteins, from a single amino acid that is altered

steroids all come from what?

cholesterol

thus are lipid soluble

Important factors impacted by water-soluble hormones vs lipid-soluble Hormones

synthesis

storage

transport

interaction with target

water-soluble hormones synthesis

Synthesized as a prohormone and converted into active

fat-soluble hormones synthesis

synthesize from cholesterol

water-soluble hormone storage

usually via intracellular vesicles

fat-soluble hormone storage

often not stored, b/c they can pass through vesicle membranes,

made on demand and use hormone binding proteins

binding proteins function

They facilitate the movement of lipid-soluble hormones through the bloodstream.

help store lipid-soluble proteins

water-soluble hormone transport

usually move freely in the blood stream

fat-soluble hormone transport

bound to plasma protein

water-soluble target cell interaction

bind to membrane receptor and often use a second messenger

fat-soluble target cell interaction

usually bind to nuclear receptor, regulates gene transcription

Name the Fat-Soluble hormones

All Steroids: aldosterone, cortisol, estrogen, progesterone, testosterone

Thyroid Hormones: T3 and T4

Amino Acid Derived Hormones

Thyroid hormones: T3, T4

Adrenal medulla hormones: epinephrine, norepinephrine

Dopamine and Serotonin

Important Peptide hormones

ADH

Insulin

Oxytocin

TSH

Catecholamines

subtype of amine hormones derived from tyrosine

Epi and Norepi

T3 and T4 mechanism of action

thyroid hormones

T3 is active form and T4 must be converted to T3

Fat soluble hormones that impact gene expression

Steroids

aldosterone, cortisol, estrogen, progesterone, testosterone

lipoprotein

bonding of molecules of fat and protein

Which organ is responsible for synthesizing cholesterol when it is not obtained from the diet?

liver

Purpose of LDL

Low-density lipoprotein

transport cholesterol from the liver to peripheral tissues/organs via the blood

Steroid Hormone Synthesis

1. Cholesterol from the diet or liver is packaged with LDL for transport in the bloodstream.

2. LDL binds to cell receptors and is taken into the cell.

3. LDL is broken down, releasing free cholesterol.

Cholesterol is converted in the mitochondria to pregnenolone, which is then used to make the specific steroid hormone needed.

Each step of steroid hormone synthesis requires what?

a functioning enzyme

Example: to make testosterone you must first produce prenenolone or progesterone or to make aldosterone you must first make corticosterone

Aldosterone

"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure

A pharmaceutical company is developing a drug to block aldosterone's effect on sodium retention. What might be the goal of this medication?

To treat hypertension by reducing blood volume

cAMP

cyclic adenosine monophosphate

Two secondary messengers for peptide hormones

cAMP & C++ release

How does cAMP function as a secondary messenager

1. The hormone binds to a receptor activating a G protein

2. G protein activates Adenyl Cyclase

3. Adenylate cyclase converts ATP into cyclic AMP (cAMP), which acts as a second messenger by activating protein kinase

4. Protein kinase phosphorylates a protein which causes a cell responce

What is the major effect of cyclic AMP (cAMP) as a second messenger?

Activates Protein Kinases

How does Ca2+ function as a secondary messenager

1. The hormone binds to a receptor activating a G protein

2. the G protein opens the Ca++ ion channel allowing Ca++ to flow in causing a cell responce

Steps of how lipid soluble hormones act on the cell

1. Hormone enters through the cell membrane and travels to the nucleus

2. It binds to a nuclear receptor that controls expression of a gene and activates expression

3. The gene is transcribed and a protein is synthesized

Nuclear receptors

Protein inside a eukaryotic cell that, on binding to a signal molecule, regulates transcription.

intracellular change = _______ change

physiological change

Negative feedback loop

A feedback loop that causes a system to change in the opposite direction from which it is moving

Hierarchical Levels Of Control

when many levels of endocrine glans and hormones are involved with the secretion of a final hormone that acts on a target organ

What would happen if hormone three in a hierarchical control system is not produced?

Negative feedback to gland one and gland two would stop, leading to increased production of hormones one and two.

What would happen if the hypothalamus is damaged reducing activity, in a hierarchical control system?

all hormones in the system would have reduced secretion due to a cascade effect of a lack of the first hormone released from the hypothalamus

What is the value of a hierachical control?

there is a lot of feedback so specific control over secretion can be kept

Hypothalamus

brain region controlling the pituitary gland

Connecting Stalk

connection between the hypothalamus and the pituitary gland

anterior pituitary gland

the anterior part of the pituitary gland

an endocrine gland whose secretions are controlled by the hypothalamic hormones

Posterior pituitary

Stores and releases hormones from hypothalamus.

Which gland is not considered a true independent endocrine gland?

posterior pituitary

Difference between the Anterior Pituitary and Posterior Pituitary

Anterior is the real endocrine gland, with secretory cells

Posterior: mostly just an extension of the hypothalamus

Neurosecretory neurons

Neurons releasing hormones into the bloodstream.

Describe the connection between the hypothalamus and posterior pituitary

1. Neurosecretory neurons leave the hypotalamus, and travel to the posterior pituitary, via the connecting stalk.

2. In the posterior pituitary the Neurosecretory neurons release hormones into the blood stream

What hormones are released in the posterior pituitary

Vasopressin (ADH)

Oxytocin

Describe the connection between the hypothalamus and anterior pituitary (AP)

1. Neurosecretory neurons leave the hypotalamus, and release hormones into the blood stream

2. The hormones travel, via blood, down the connecting stalk to the AP

3. The hormones stimulate endocrine cells in the AP to produce hormones which are released into blood circulation and travel to target organs

What hormones are produced by the anterior pituitary gland

TSH, ACTH, Prolactin, GH, LH, FSH

TSH

thyroid stimulating hormone

Stimulates the Thyriod glad and produce T3 and T4

Thyrotrophs

secrete thyroid stimulating hormone (TSH)

ACTH

adrenocorticotropic hormone

Stimulates the Adrenal cortex to release cortisol

Prolactin

stimulates milk production and mammary gland growth

Prolactin and Dopamine dynamic

dopamine inhibits the release of prolactin

GH

growth hormone

stimulates liver and many other tissues

LH and FSH

luteinizing hormone & Follicle-Stimulating Hormone

stimulate ovaries/testes

Lacotrophs

secrete prolactin (PRL)

Gonadotrophs

secrete FSH and LH

corticotroph cells

Pituitary cells producing ACTH.

What hormone from the hypothalamus stimulates FSH/LH release

Gonadotropin-Releasing Hormone (GnRH)

What hormone from the hypothalamus stimulates ACTH release

Corticotropin-Releasing Hormone (CRH)

What hormone from the hypothalamus stimulates TSH release

Thyrotropin-Releasing Hormone (TRH)

What hormone from the hypothalamus stimulates Prolactin release

Prolactin-Releasing Hormone (PRH)

When is Prolactin-Releasing Hormone (PRH) released?

During childbirth and breast/chest feeding to stimulate milk production

What hormone from the hypothalamus inhibits Prolactin release

dopamine

What hormone from the hypothalamus stimulates GH release

Growth Hormone-Releasing Hormone (GHRH)

What hormone from the hypothalamus inhibits GH release

Somatostatin

What type of cells release GH

Somatotrophs in the anterior pituitary

When is GH released?

During deep sleep: stage II non-rem sleep

GH effects

acts on the liver to produce IGF 1 and 2

increases the availability of glucose in the blood stream

IGF 1 and 2

Insulin-like Growth Factor

Acts similar to insulin by allowing cells to take up the glucose, that was released by GH, and use the glucose to grow and divide

A patient presents with low levels of IGF-1 but normal levels of growth hormone. What might be malfunctioning?

liver

When is IGF released?

in opposite cycle of GH

When GH is low IGH is high, during sleep

Impact of GH + IGH on cells

increases linear bone growth

increases organ size

decreases adiposity

increases lean body mass

allows for increased cell division

General maintenance of tissue

Thyroid gland

produces hormones that regulate metabolism, body heat, and bone growth

Cell structures of the thyroid gland

- arranged in follicles

- within the follicles is a protein material called colloid

- follicular cells produce thyroid hormones and store them in the colloid with thyroglobulin

- C-cells and blood capillaries are between the follicles

thyroglobulin

secreted by follicle cells

binds with iodine to produce T4 and T3 and makes up colloid

C-cells

produce calcitonin which controls calcium levels in the body

Production pathway from hypothalamus to T3/4 release

Hypothalamus => TRH release => anterior pituitary stimulation => TSH release => thyroid stimulation => T3/4 release => target organ stimulation

Impact of T3 and T4 in the body

increase the production of proteins that require energy (ATP) so it increases metabolic rate

- increased Metabolic rate and heat production

- enhancement of growth and CNS development

- enhancement of sympathetic activity

Is T3/T4 release continuous or on an as needed basis

continuous controlled release

Adrenal gland

A pair of endocrine glands that sit just above the kidneys and secrete hormones that help arouse the body in times of stress.

adrenal cortex location

outer section of each adrenal gland

adrenal cortex secretes what hormones

secretes cortisol, aldosterone, and sex hormones