Flashcards in Intro to Endocrine Deck (56):
Common endocrine diseases managed by the primary care provider?
- diabetes mellitus
- thyroid diseases (hypothyroidism and hyperthyroidism)
What is endocrinology?
- study of hormones and disorders of these hormones
What makes up the endocrine system?
- hypothalamus and pituitary
- thyroid and parathyroid
- (islets of langerhans, ovaries, testicles, placenta)
Who was the first person to use the term hormone?
- Ernest Henry Starling
How does the endocrine system maintain homeostasis?
- hormones act on distant target cells to maintain the stability of the internal environment
- secretion of the hormone was evoked by a change in the milieu and the resulting action on the target cell restored the milieu to normal. The desired return to the status quo results in the maintenance of homeostasis
What are hormones?
- any substance normally produced by specialized cells in some part of the body, carried by the blood stream to another part, where it effects the body as a whole
- vehicles for intracellular and extracellular communication
What are the functions of hormones?
- maintain homeostasis
- regulate growth and development
- promote sexual maturation, sexual rhythms and facilitate reproduction
- regulate energy production
- adapt/adjust body to stressful/emergency situations
- promote/inhibit production or release of other hormones
What are the characteristics of hormones?
- specificity: only target cells respond
- multiple actions
- varibale half life: often depends on solubility properties
- variable forms: depends on wt
- excretion rates: diurnal variation, cyclic patterns, and stimulus response
What are the 2 different functional types of hormones?
- tropic: originate from anterior pituitary gland
specific for another endocrine gland
- non-tropic or direct effector: secreted by non-pituitary endocrine glands, act directly on peripheral tissue. Exert a feedback effect on hypothalamus or anterior pituitary gland
categories of chemical hormones?
- peptides/proteins: polypeptides or glycoproteins, soluble in plasma, interact with target cell membrane receptors to trigger a 2nd messenger to complete the specific action of the hormone, short term effects
- Amines: AA derivatives, poorly soluble in plasma, interact with membrane receptors of target cells, provide long and short term effects
- steroids: composed of lipids (cholesterol), can transverse through the cell membrane, produced by ovaries, testis, placenta, and adrenal cortex, insoluble in water, and long-lasting
Where are hormone receptors and what are their function?
- located on cell membrane or within cell cytoplasm.
- binding of hormone to receptor initiates a signal, results in changes in gene expression, ultimately causes a biological response.
How are hormones regulated and controlled?
- occurs by controlling rate of synthesis rather than rate of degradation
- primary control: hypothalamus - small gland next to pituitary gland, and is connected to pituitary by "pituitary stalk"
- pituitary gland: releases both tropic and effector hormones
Relationship b/t endocrine and nervous system?
- 2 major communication systems in the body
- integrate stimuli and responses to changes in external and internal environment
- both are crucial to coordinated functions of highly differentiated cells, tissues, and organs
- unlike the nervous system, the endocrine system is anatomically discontinuous.
Functions of the nervous system?
- exerts point-to-point control through nerves, similar to sending messages by conventional landline telephone. Nervous control is electrical in nature and immediate
Endocrine system functions?
- broadcasts its hormonal messages to essentially all cells by secretion into blood and extracellular fluid. Like a radio broadcast, it requires a receiver to get the message, in the case of endocrine messages, cells must bear a receptor for the hormone being broadcast in order to respond.
Why are cells targets for hormones?
- becausae it has a specific receptor for the hormone
- most hormones circulate in blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called target cells, a target cell responds to a hormoned because it bears receptors for the hormone
What 2 systems are needed for proper body regulation and function?
- Nervous system and Endocrine system
Breakdown of Nervous system?
- PNS: Efferent and Afferent, efferent: Autonomic (parasympathetic and sympathetic) , and somatic
Are the 2 main systems (endocrine and nervous system) that coordinate and regulate function mutually exclusive?
- one example of 2 systems working together: sympathetic flight or fight response - direct stimulation of effector site by neuron -> stimulation of medulla results in release of epi and norepi in the blood which: greatly prolongs sympathetic stimulation, and this can affect all cells of the body, even those not innervated directly by sympathetic neurons
2 major regulatory systems of the body?
- endocrine and nervous system
- **** Because there is so much overlap with coordination of function with the nervous system, there are several sxs of endocrine disorders that mimic pathology seen in other organ systems
What does the endocrine system do?
- controls numerous body processes:
growth and development
- involves numerous organs and tissues located throughout the body, and it works in conjunction with the nervous system (and to lesser extent with the immune system)
- produces chemical messengers (hormones) that influence growth, development, and metabolic activities. There are 2 major categories of glands in the body: exocrine and endocrine
What are hormones?
- chemical messengers that are released in one tissue and transported by bloodstream to reach target cells in their tissues
What are exocrine glands?
- produce secretions which are released to the outside; the sweat, salivary, mammary, and digestive gland systems are examples of this.
- hormones are secreted directly into the blood and are carried throughout the body where they influence the appropriate receptor sites for that hormone.
What are mixed glands?
- (both exocrine and endocrine), some glands have non-endocrine regions that have functions other than hormone secretion. For example, the pancreas has a major exocrine portion that secretes digestive enzymes and an endocrine protion that secretes hormones
Components of the endocrine system?
- pineal gland
- pituitary gland
- thyroid gland
- parathyroid glands
- adrenal glands
Function of the hypothalamus?
- primary link b/t endocrine and nervous systems
- regulates activities of nervous and endocrine systems in 3 ways: 1- acts as an endocrine organ and releases hormones ADH and oxytocin
2 - secretes regulatory hormones (releasing hormones or inhibiting hormones)
3- control endocrine cells in the adrenal medulla
Pituitary gland structure?
- AKA hypophysis
- small oval gland seated in sella turcica of sphenoid bone
- consists of 2 lobes (anterior and posterior)
anterior: adenohypophysis (made up of glandular cells)
posterior: neuroypophysis (cells are non-secretory, resemble neurological tissue)
Function of adenohypophysis?
- can be divided into anterior pars distalis and posterior pars intermedia
- contains endocrine cells surrounded by an extensive capillary network (hypophyseal portal system)
- secretes 7 important hormones, and 6 are produces by the pars distalis
Hormones of adenohypophysis?
- thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone (FSH)
- luteinizing hormone (LH)
- Prolactin( PRL)
- Somatotrophin (GH)
- melanocyte-stimulating hormone (MSH)
What does the neurohypophyis (posterior lobe of pituitary gland) produce?
- contains the axons of hypothalamic neurons
- nuclei of hypothalamus produce ADH and oxytocin
Which lobe secretes more hormones?
- anterior lobe (adenohypophysis)
WHat is the pineal gland, fxn?
- lies in the roof of the thalamus (3rd ventricle), under teh posterior end of the corpus callosum
- it contains neurons, glial cells, and secretory cells that synthesize the hormones melatonin
Where is the thyroid gland, function?
- lies anterior to trachea and just below thyroid cartilage, which forms most of anterior surface of larynx
- Has 2 lobes (butterfly shape) united by isthmus
- has an extensive blood supply
- produces the hormones T3, T4, and calcitonin
Where are parathyroid glands located and what are their functions?
- 2 pairs of parathyroids embedded in the posterior surface of thyroid gland
- there are 2 different types of cells within parathyroid glands (chief cells and oxyphil cells)
- Chief cells produce parathyroid hormone (parathormone) -> stimulates osteoclasts, inhibits osteoblasts, increases intestinal absorption, and reduces urinary exretion of calcium ions
- Oxyphil cell function: unknown, but appears at onset of puberty
Where is the thymus and what is the function?
- embedded in the mediastinum, usually posterior to the sternum
- organized in 2 lobes separated by septa. Each lobe consists of dense outer cortex and central medulla
- cortex consists of epithelial cells that secrete thymic hormones (Thymosins= T cells), which play key role in development and maintenance of immunological defenses
- medulla has thymic corpuscles (Hassall's corpuscles): unknown function
Adrenal gland location and function?
- AKA suprarenal glands
- lie along superior borders of kidneys
- pyramid shaped glands
- can be subdivided on histological grounds into an outer cortex and inner medulla
Adrenal cortexL produces steroid hormones called corticosteroids, contains 3 distinct zones, and has yellowish color due to presence of stored lipids
Where are corticosteroids produced?
- adrenal cortex -> of adrenal glands
What are the zones of adrenal cortex?
- zona glomerulosa (outermost and relatively narrow layer, secretes mineralocorticosteroids: aldosterone)
- zona fasciculata: extends toward the capsule in a series of radiating cell columns. Produces glucocorticoids (cortisol, corticosterone, and cortisone)
- zona reticularis: surrounds adrenal medulla, produces androgens
- adrenal medulla: contains 2 populations of secretory cells, one produce epi (75-80%) and the other NE (20-25%)
- contains exocrine and endocrine cells
- endocrine cells are found within pancreatic islets (islets of langerhans)
alpha cells: secrete glucagon - released when glucose levels are too low
beta cells: produce insulin - released when glucose levels too high
Gonads males and females?
- testes: male gonads, located in scrotum
each testicle is made up of seminiferous tubules which produce spermatozoa, b/t tubules are interstitial cells that secrete steroid hormones known as androgens (testosterone)
- ovaries: female sex organs, located in pelvic cavity, follicle cells in the ovaries produce steroid estrogens while eggs are developing. After ovulation the cells reorganize into a corpus luteum that produces progesterone. If a pregnancy occurs, the placenta will gradually develop endocrine functions on its own.
What are the non-endocrine organs that produce hormones?
also produce and release hormones
How are diseases and disorders of the endocrine system characterized?
- hypo or hyper hormone release
- inappropriate response to signaling
- absence of a gland
- structural enlargement
How are diseases and disorders of endocrine system classified?
primary: inhibits action of downstream glands
secondary: indicative of problem with pituitary gland
tertiary: dysfunction of hypothalamus
What are the adrenal insufficiency disorders?
- addison's disease (primary adrenal insufficiency)
- mineralocorticoid deficiency
What are the adrenal hormone excess disorders?
- conn's syndrome (aldosterone producing adenoma)
- cushing's syndrome (high levels of cortisol in the blood by a tumor or systemic steroids)
- GRA/glucocorticoid remediable aldosteronism (cause of primary hyperaldoesteronism)
- congenital adrenal hyperplasia
- adrenocortical carcinoma
What are the pancreas disorders?
- diabetes mellitus: type 1, type 2, and gestational diabetes
- hypoglycemia: idiopathic hypoglycemia, insulinoma (tumor of the b-cells in the pancreas)
- Glucagonoma: tumor of the iselt cell in the pancreas
- goiter (iodine deficiency)
- hyperthyroidism: graves disease, and toxic multinodular goiter
- thyroiditis: hashimoto's thyroiditis
- thyroid cancer
- parathyroid gland disorders: primary hyperparathyroidism, secondary hyperparathyroidism, tertiary hyperparathyroidism, and hypoparathyroidism (pseudohypoparathyroidism)
- osteitis deformans (Paget's disease of the bones)
- Rickets and osteomalacia
Pituitary gland disorders?
- posterior pituitary: diabetes insipidus
- anterior pituitary: hypopituitarism, pituitary tumors: pituitary adenomas, prolactinoma (hyperprolactinemia), acromegaly, gigantism, cushing's disease
categories of sex hormone disorders?
-disorders of sex development
- hypogonadism (gonadotropin deficiency)
Disorders of sex development?
- gonadal dysgenesis
- androgen insensitivity syndromes
-inherited (genetic and chromosomal disorders): kallmann syndrome, klinefelter syndrome, turner syndrome
- disorders of puberty: delayed puberty, precocious puberty
- menstrual function or fertility disorders: amenorrhea, and polycystic ovary syndrome
Tumors of endocrine glands?
- Multiple endocrine neoplasia:
MEN 1: parathyroid, pancreatic, and pituitary
MEN 2: thyroid, pheochromocytoma, parathyroid
MEN 3: medullary thyroid cancers, pheochromocytoma, neuroma
- carcinoid syndrome