Endocrine Organs

Hormone

Mechanism

Paracrine

Autocrine

Endocrine

Compounds

Steroid

Amino acids and arachidonic acid analogs

Peptides and proteins

Luteinizing hormone (LH)

Antidiuretic hormone (ADH)

Follicle-stimulating hormone (FSH)

Oxytocin

Adrenocorticotropic hormone (ACTH)

Interleukins

Growth hormone (GH)

Glucagon

Various growth factors

Insulin

Gonadal steroids

Adrenocortical steroids

Prostaglandins

Prostacyclins

Catecholamines

Leukotrienes

Thyroid hormones

Epinephrine

Norepinephrine

Receptor

Cell surface receptors

Intracellular receptors

Regulation

Positive feedback

Negative feedback

Pituitary gland (Hypophysis)

Thyroid gland

Pineal gland

Adrenal glands

Parathyroid glands

Hypothalamus

Gross structure

Anterior lobe (adenohypophysis)

Posterior lobe (neurohypophysis)

Embryologic origin

Ectoderm of the oropharynx

Rathke's pouch

Composition

Pars distalis

Pars intermedia

Pars tuberalis

Embryologic origin

Composition

Neuroectoderm of the floor fo the third ventricle (diencephalon)

Pars nervosa

Infundibulum

Forms hypothalamohypophyseal tracts

Blood supply

Superior hypophyseal arteries

Inferior hypophyseal arteries

Continuous with median eminence

Arise from internal carotid arteries

Supply

Pars tuberalis

Median eminence

Infundibulum

Arise from internal carotid arteries

Supply pars nervosa

Tropic hormones

ACTH

Thyroid-stimulating hormone (TSH)

FSH

LH

Lactotropes (PRL cells, mammotropes)

Corticotropes (ACTH cells)

Somatotropes (GH cells)

Gonadotropes (FSH, LH cells)

Thyrotropes (TSH cells)

Follicular stellate cells

Star-like

Form cell clusters or small follicles

Do not produce hormones

Interconnected with connexin-43

Small cystic cavities

Parenchymal cells

Lining on the colloid follicles

Derived from folliculo-stellate cells or hormone secreting cells

Function unclear

Highly vascular region

Herring bodies

Hormones

Oxytocin

ADH

Location

Middle of the base of brain

Encapsulates ventral portion of 3rd ventricle

Functions

Major controlling centers of autonomic nerve system

Coordinates endocrine function

Hormones

Dopamine

Corticotropin-releasing hormone (CRH)

Somatostatin

Gonadotropin-releasing hormone (GnRH)

Growth hormone-releasing hormone (GHRH)

Thyrotropin-releasing hormone (TRH)

Regulates daily rhythm

Developed from neuroectoderm of posterior portion of roof of diencephalon

Located at posterior wall of 3rd ventricle

Melatonin

Corpora arenacea (Brain sand)

Parenchymal cells

Pinealocytes

Interstitial (glial) cells

Chief cells

Large deeply infolded nucleus

lipid droplets in cytoplasm

Light impulse inhibits production of melatonin

Inhibits gonadal hormone release (Inhibit GnRH release)

Features

Bilobate connected by isthmus

In anterior neck region adjacent to larynx and trachea

Thyroid follicle

Colloid

Epithelium

Functional unit

Enzymes

Glycoproteins

Thyroglobulin

Inactive storage form of hormone

Follicular cells (Principle cells)

Parafollicular cells (C cells)

Lipid droplets and PAS-positive droplets

Both secretory and absorptive cell morphology

Slightly basophilic

Produces T3 (Triiodothyronine), T4 (Tetraiodothyronine)

No exposure to the follicle lumen

Secrete calcitonin (thyrocalcitonin)

Located in the periphery of epithelium

Essential to normal growth and development

Antagonist to parathyroid hormone (PTH)

Suppressing osteoclasts

Regulated by blood calcium levels

Regulate cell and tissue metabolism, heat production

Influence body growth and development

Regulated by TSH from anterior pituitary

Poorly defined lobules

Essential for life

Epithelial cells

Principle (Chief) cells

Oxyphil cells

Small, polygonal cells with centrally located nucleus

Synthesis, storage and secretion of PTH

Major type of parenchymal cells

Round, larger than principle cells

Acidophilic cytoplasm

Parathyroid hormone-related protein (PTHrP)

Secretory parenchymal tissue

Cortex (Steroid secreting)

Medulla (Catecholamine secreting)

Norepinephrine

Blood supply

Fenestrated cortical sinusoidal capillaries

Medullary arterioles

Capsular capillaries

Zonation

Zona fasciculata

Zona reticularis

Zona glomerulosa

Closely packed ovoid clusters

small and columnar or pyramidal cells

15% cortical volume

large and polyhedral cells

Long straight cords, separated by sinusoidal capillaries

80% cortical volume

5-7% cortical volume

Arranged anastomosing cords, separated by fenestrated capillaries

Glucocorticoids

Gonadocorticoids

Mineralocorticoids

Epinephrine

Aldosterone

Corticosterone

Cortisol (major)

Dehydroepiandrosterone (DHEA)

Dehydroepiandrosterone sulfate (DHEAS)

Androstenedione

Cells of adrenal medulla

Chromaffin cells

Ganglion cells

Modified neurons

Lacking axonal process

Pale-stained epithelioid cells

Large polygonal cells

Located closely to adrenomedullary vein