Endocrine System Flashcards
consists of axons extending from the hypothalamic supraoptic and para- ventricular nuclei, through the infundibulum and into the pars nervosa of the posterior pituitary, where peptide hormones they carry are released for capillary uptake
hypothalamic-hypophyseal tract
consists of two capillary networks connected by the hypophyseal portal vein. The primary plexus surrounds the infundibulum and median eminence, and the second is throughout the pars distalis and drains into the hypophyseal veins
hypothalamic-hypophyseal portal system
- 50
- Somatotropin (growth hormone, GH), a 22-kDa protein
- Stimulates growth in epiphyseal plates of long bones via insulin-like growth factors (IGFs) produced in liver
Somatotrophs
- 15-20
- Prolactin (PRL), a 22.5-kDa protein
- Promotes milk secretion
Lactotrophs (or mammotrophs)
- 10
- Follicle-stimulating hormone (FSH) and luteinizing hormone (LH; interstitial cell- stimulating hormone [ICSH] in men), both 28-kDa glycoprotein dimers, secreted from the same cell type
- FSH promotes ovarian follicle development and estrogen secretion in women and spermatogenesis in men; LH promotes ovarian follicle maturation and progesterone secretion in women and interstitial cell androgen secretion in men
Gonadotrophs
- 5
- Thyrotropin (TSH), a 28-kDa glycoprotein dimer
- Stimulates thyroid hormone synthesis, storage, and liberation
Thyrotrophs
- 15-20
- Adrenal corticotropin (ACTH), a 4-kDa polypeptide
- Lipotropin (LPH)
- Stimulates secretion of adrenal cortex hormones
- Helps regulate lipid metabolism
Corticotrophs
TRH, PRH, GnRH, CRH, GHRH
Releasing hormones
PIH, GIH
Inhibiting hormones
stimulates the thyroid gland to release thyroid hormone
Thyroid-stimulating hormone (TSH)
acts on mammary glands to stimulate milk production
prolactin (PRL)
act on gonads (testes and ovaries) to stimulate development of gametes (sperm and oocyte)
Follicle-stimulating hormone (FSH)
and luteinizing hormone (LH)
acts on all body tissues, especially cartilage, bone, muscle, and adipose connective tissue to stimulate growth
growth hormone (GH)
acts on the adrenal cortex to cause release of corticosteroids
adrenocorticotropic hormone (ACTH)
- 3-amino acid peptide
- Stimulates release of thyrotropin (TSH)
Thyrotropin-releasing hormone (TRH)
- 10-amino acid peptide
- Stimulates the release of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Gonadotropin-releasing hormone (GnRH)
- 14-amino acid peptide
- Inhibits release of both somatotropin (GH) and TSH
Somatostatin
- 40- or 44-amino acid polypeptides (2 forms)
- Stimulates release of GH
Growth hormone-releasing hormone (GHRH)
- 40- or 44-amino acid polypeptides (2 forms)
- Stimulates release of GH
Growth hormone-releasing hormone (GHRH)
- Modified amino acid
- Inhibits release of prolactin (PRL)
Dopamine
- 41-amino acid polypeptide
- Stimulates synthesis of pro-opiomelanocortin (POMC) and release of both β-lipotropic hormone (β-LPH) and corticotropin (ACTH)
Corticotropin-releasing hormone (CRH)
Increases water permeability of renal collecting ducts
Vasopressin/antidiuretic hormone (ADH)
Stimulates contraction of mammary gland myoepithelial cells and uterine smooth muscle
Oxytocin
adversely affected by heritable mutations in the gene for vasopressin (ADH)-neurophysin, by compression from a tumor in adjacent tissues, and by head trauma
posterior pituitary function
- autoimmune in origin
- degeneration in any layer of adrenal cortex, with concomitant loss of glucocorticoids, mineralocorticoids, or androgen production
Addison disease or adrenal cortical insufficiency
rounded clusters of columnar or pyramidal cells principally secreting the mineral corticoid aldosterone. Blood-filled regions are parts of the subcapsular arterial plexus
zona glomerulosa
consists of long cords of large, spongy-looking cells mainly secreting glucocorticoids such as cortisol
zona fasciculata
have fewer lipid droplets and are therefore better stained, arranged in a close network and secrete mainly sex steroids, including the androgen precursor DHEA
zona reticularis
loss of the insulin effect and a subsequent failure of cells to take up glucose, leading to elevated blood sugar or hyperglycemia
diabetes mellitus
caused by loss of the β cells from autoimmune destruction and is treated by regular injections of insulin
Type 1 diabetes or insulin-dependent diabetes mellitus (IDDM)
- β cells are present but fail to produce adequate levels of insulin in response to hyperglycemia and the peripheral target cells “resist” or no longer respond to the hormone
- occurs with obesity, and poorly understood, multifactorial genetic components are also important in this disease’s onset
type 2 diabetes or non–insulin- dependent diabetes mellitus (NIDDM),
clumped masses of pale-staining endocrine cells embedded in the exocrine acinar tissue of the pancreas
Pancreatic islets
- ~20
- Glucagon
- Polypeptide; 3500 Da
- Acts on several tissues to make energy stored in glycogen and fat available through glycogenolysis and lipolysis; increases blood glucose content
α
- ~70
- Insulin
- Dimer of α and β chains with S-S bridges; 5700-6000 Da
- Acts on several tissues to cause entry of glucose into cells and promotes decrease of blood glucose content
β
- 5-10
- somatostatin
- Polypeptide; 1650 Da
- Inhibits release of other islet cell hormones through local paracrine action; inhibits release of GH and TSH in anterior pituitary and HCl secretion by gastric parietal cells
δ or D
- Rare
- Pancreatic polypeptide
- Polypeptide; 4200 Da
- Stimulates activity of gastric chief cells; inhibits bile secretion, pancreatic enzyme and bicarbonate secretion, and intestinal motility
PP
inhibit thyroid hormone production, causing thyrotropic cells of the anterior pituitary gland to produce excess TSH
Chronic dietary iodine deficiencies
autoimmune disorder in which antibodies produce chronic stimulation of the follicular cells and release of thyroid hormones (hyperthyroidism), which causes a hyper- metabolic state marked by weight loss, nervousness, sweating, heat intolerance, and other features
graves disease
- reduced thyroid hormone levels
- local inflammation (thyroiditis) or inadequate secretion of TSH by the anterior pituitary gland and is often manifested by tiredness, weight gain, intolerance of cold, and decreased ability to concentrate
Hypothyroidism
diminished secretion of PTH can cause bones to become more mineralized and denser and striated muscle to exhibit abnormal contractions due to inadequate calcium ion concentrations
hypoparathyroidism
- Adrenal glands: Cortex
- Mineralocorticoid
- Stimulate renal reabsorption of water and Na+ and secretion of K+ to maintain salt and water balance
Cells of zona glomerulosa
- Adrenal glands: Cortex
- Glucocorticoids
- Influence carbohydrate metabolism; suppress immune cell activities
Cells of zona fasciculata
- Adrenal glands: Cortex
- Weak androgens
- Precursors for testosterone or estrogen
Cells of zona reticularis
- Adrenal glands: Medulla
- Chromaffin cells
- Increases heart rate and blood pressure
Epinephrine
- Adrenal glands: Medulla
- Chromaffin cells
- Constricts vessels; increases heart rate and blood pressure
Norepinephrine
- Pancreatic islets
- Glucagon
- Raises blood glucose levels
α Cells
- Pancreatic islets
- Insulin
- Lowers blood glucose levels
β Cells
- Pancreatic islets
- Somatostatin
- Inhibits secretion of insulin, glucagon, and somatotropin
δ Cells
- Pancreatic islets
- Pancreatic polypeptide
- Inhibits secretion of pancreatic
enzymes and HCO –
PP cells
- Thyroid glands
- Thyroid hormones (T3 and T4)
- Increases metabolic rate
Follicular cells
- Thyroid glands
- Calcitonin
- Lowers blood Ca2+ levels by inhibiting osteoclast activity
Parafollicular or C cells
- Chief cells
- Parathyroid hormone (PTH)
- Raises blood Ca2+ levels by stimulating osteoclast activity
Parathyroid glands
- Pinealocytes
- Melatonin
- Regulates circadian rhythms
Pineal gland
pars nervosa develops as a downgrowth of the developing brain and is attached in the hypothalamus by the infundibulum
posterior pituitary
pars distalis, the pars tuberalis that surrounds the infundibulum, and the thin pars intermedia adjacent to the pars nervosa
anterior pituitary
important in carrying peptide factors from hypothalamic neurons to cells of the anterior pituitary where they control cell secretion
hypothalamic hypophyseal portal system
Endocrine cells of the anterior pituitary can be called ___, ___, or ___ based on their general staining prop- erties; the latter lack secretory granules and stain poorly
acidophils; basophils; chromophobes
which pituitary hormone they produce using immunohistochemistry and
antibodies against specific hormones
Acidophils and basophils
primarily somatotrophs producing somatotropin (growth hormone), or lactotrophs (or mammotrophs)
producing prolactin (PRL)
Acidophils
gonadotrophs producing FSH and LH and
thyrotrophs making TSH
Basophils
corticotroph, synthesizing POMC that is cleaved by proteases to make ACTH and β-LPH
third type of basophil
bundles of nerve axons that run from supraoptic nucleus (SON) and paraventricular nucleus (PVN) in the hypothalamus to the posterior pituitary
hypothalamic hypophyseal tract
consists of three concentric zones, all histologically distinct but with cells producing steroid hormones and all drained by the same system of capillaries
adrenal cortex
- most superficial
- round clusters of cells producing mineralocorticoids such as aldosterone regulating electrolyte levels
zona glomerulosa
elongated strands of cells producing glucocorticoids such as cortisol, which regulates several aspects of carbohydrate metabolism
zona fasciculata
network of cells making the weak androgen DHEA that is converted to testosterone in men and women
zona reticularis
contains neural crest-derived chromaffin cells synthesizing either epinephrine or norepinephrine that regulate the stress response
adrenal medulla
small clusters of pale cells embedded within the exocrine tissue; they have primarily β cells making insulin, α cell (glucagon), and δ cells (somatostatin)
Pancreatic islets of Langerhans
consists mainly of spherical follicles composed of simple epithelium of thyrocytes surrounding a lumen with thyroglobulin
thyroid gland
large glycoprotein in which tyrosine residues are iodinated as precursors of the thyroid hormones thyroxine and triiodothyronine, which are released when the precursor is degraded
Thyroglobulin
- Thyroid follicles also contain a few smaller and paler cells called
- C cells
- produce the polypeptide hormone calcitonin
parafollicular cells
- On the posterior side of the thyroid glands are four small ___
- consisting primarily of principal cells that secrete PTH that raises blood Ca2+ levels
parathyroid glands
develops from embryonic neuroectoderm, remains attached to the brain, and contains modified neurons called pinealocytes that secrete the amine melatonin
pineal gland
- Pineal landmarks are the concretions called ___
- brain sand
corpora arenacea
- neural connections from the retina to ___ allow diurnal secretion of melatonin and rhythms in physiological activities
pinealocytes
Are produced in response to stimulation by ACTH
glucocorticoids
Pregnant women who have begun labor but in whom this process is no longer progressing are often given an IV injection of Pitocin to stimulate uterine contractions and facilitate parturition. Pitocin is a trade name of a hormone produced in what endocrine tissue?
Pars nervosa
What hormone is produced in response to decreased blood calcium levels?
PTH
Addison disease (or adrenal cortex insufficiency) is a disorder, usually autoimmune in origin, which can cause degeneration and cell loss in the adrenal glands. Fludrocortisone is a mineralocorticoid used to treat Addison patients. Response to this drug indicates that which region of the adrenal glands was involved in the disease?
Zona glomerulosa
A glucagonoma is a malignant tumor consisting of what cells?
A or α cells
Secretion, chemical modification and storage, reuptake, and digestion of a protein occur in epithelial cells of what endocrine tissue?
Thyroid gland
Secretion in what neuroendocrine cell is controlled directly by neural activity and involves a hormone that generally slows metabolic activity at night?
Pinealocyte
Some mammalian endocrine tissues or cells can be experimentally transplanted to other well-vascularized sites (such as the oral mucosa) in genetically similar hosts and the tissue’s function continues normally and with proper regulation. The pars distalis is not a good candidate for such transplantation studies for which one of the following reasons?
Its cells stop functioning when separated from the hypothalamo-hypophyseal portal system
A 45-year-old corporate executive presents with the primary com- plaint of “always being tired.” She comments that she has been tired for 4 months even though she is sleeping more. She complains of being unable to finish chores at home and “dragging at work.” She indicates that she is often constipated and is intolerant of cold. She is continuously turning the thermostats in the house and office to higher temperatures, to the dismay of family and coworkers. She also complains that her skin is very dry; use of lotions and creams have not helped the dryness. A biopsy of her thyroid gland shows dense lymphocytic infiltration with germinal centers throughout the parenchyma and a battery of further tests is carried out, which also suggest thyroiditis. Which of the following results of blood tests would be most likely in this patient?
Elevated TSH levels
A 9-year-old girl, the youngest of four daughters, is taken to the pediatrician by her mother, who indicates that for at least 4 months the child has seemed “hyperactive,” unable to sleep soundly because “she says her room is too hot,” and no longer able to concentrate in school. Upon questioning, the mother also remembers that her daughter’s periods also began within the past few months. Blood tests indicate high levels of estrogen-related hormones and cortisol. Which of the following tentative diagnoses is consistent with all of these symptoms?
A benign tumor involving cells in the adenohypophysis
