Flashcards in Cobine: The Pituitary and Hypothalamus Deck (98):
The (blank) is a portion of the brain located just inferior to the thalamus
The pituitary measures ~1 cm in diameter and is located in the (blank)
How is the hypothalamus connected to the pituitary?
via the pituitary stalk (infundibulum)
The hypothalamus serves many neural functions and plays an important role in connecting the nervous system to the (blank) and regulating (blank)
endocrine system; regulating pituitary function
Six hormones released by the hypothalamus
GRHR, GnRH, SS, TRH, DA, CRH
Two lobes of the pituitary gland
anterior lobe (adenohypophysis)
posterior lobe (neurohypophysis)
During embryo development, the two lobes of the pituitary gland originate from different sources. What does the anterior lobe originate from? The posterior lobe?
anterior: an invagination of the pharyngeal apithelium (Rathke's pouch)
posterior: from a neural tissue outgrowth from the hypothalamus
Secretion by the anterior pituitary is controlled by hormones secreted by neurons within the (blank)
Secretion from the posterior pituitary is from (blank) which originate in the hypothalamus and terminate in the posterior lobe.
2 major cell types of the anterior pituitary gland
2 major acidophils in the anterior pituitary gland. Which is more abundant, and what do they secrete?
somatotropes (40%) - secrete growth hormone; lactotropes (20%) - secrete prolactin
3 major basophils in the anterior pituitary gland. Which is most abundant, and what do they secrete?
1. corticotropes (20%) - secrete adrenocorticotropic hormone (ACTH)
2. thyrotropes (5%) - secrete thyroid stimulating hormone (TSH)
3. gonadotropes (5%) - secrete FSH and LH
Three hormone types
1. peptide and protein
Ex. of peptide/protein hormones
ACTH, ADH, oxytocin
Ex. of tyrosine-derived hormones
thyroid hormones, catecholamine hormones
Ex. of steroid hormones
glucocorticoids, mineralocorticoids, sex hormones
Which type of hormone makes up the majority of hormones?
Peptide and protein hormones are synthesized as (blank) and require (blank)
preprohormones; post-translational processing
What is the half life of a typical peptide hormone?
Steps in protein hormone synthesis
1. formation of preprohormone- chain directed to ER lumen by a signal sequence
2. enzymes chop off signal sequence to generate prohormone
3. prohormones from ER to golgi
4. secretory vesicles with enzymes chop the prohormone into active peptides
5. contents released into extracellular space
6. hormone free in circulation to reach its target
What does post-translational modification of AA do to them? Where does it occur?
alters their function and structure; occurs in the ER, Golgi, and secretory vesicles
Some examples of post-translational modification
cleavage - removal of AA's, or generating multiple copies of the same hormone
attachment of other biochemical groups (ex: carbohydrates)
changing the chemical nature of the AA
changing the structure (removal of disulfide bridges)
3 families of anterior pituitary hormones
1. glycoprotein family
2. growth hormone/prolactin family
3. pro-opiomelanocortin family (POMC)
3 hormones in the glycoprotein family
1. Thyroid stimulating hormone (TSH)
2. Lutenizing hormone (LH)
3. Follice-stimulating hormone (FH)
Glycoproteins have two subunits - what are they? Which is common to all? Which is unique?
alpha and beta; alpha common to all; beta unique
What determines the hormone half life of the glycoprotein family hormones?
greater degree of glycosylation
3 hormones in the glycoprotein family. What is their target and their major action?
1. Thyroid stimulating hormone
2. Follicle stimulating hormone
3. Lutenizing hormone
1. thyroid gland - increases synthesis of thyroid hormones
2. ovary/testes - increases folliculogenesis and estrogen synthesis in ovaries and sperm maturation in testes
3. ovary/testes - increases ovulation, formation of corpus luteum, estrogen, and progesterone synthesis in ovaries and increases testosterone in testes
Growth hormone and prolactin are (blank) hormones
There are three different forms of prolactin; Which is biologically active?
little, big, and bigbig; little
2 hormones in growth hormone/prolactin family. What is their target and their major action?
1. growth hormone
1. most tissues - growth, IGF-1 production, protein synthesis, decreased glucose utilization, and increased fat utilization
2. mammary glands and hypothalamus - increase milk secretion, growth of mammary glands, decreased GnRH
What is unique about growth hormone that sets it apart from other anterior pituitary hormones?
Growth hormone does not function through a target gland - it exerts its effect directly on almost all tissues of the body
Growth hormone causes growth of body organs, skeletal grown and increased metabolism. Discuss each.
1. increased size/number of cells in organs
2. increased growth of epiphyseal cartilage, conversion of cartilage to new bone, bone thickening, bone remodeling
3. increased protein synthesis, fat utilization, and glucose production by liver; decreaed protein breakdown, glucose uptake and utilization
Some growth effects of GH are mediated by (blank)
insulin-like growth factors (IGFs)
Where are IGFs produced? What is their indirect effect? What is the most important IGF?
in liver and at site of action; bone elongation through stimulation of osteoclasts/chondrocytes; somatomedin C
How is GH regulated?
Hypothalamus secreted growth hormone releasing hormone (GHRH) and GHIH or somatostatin to inhibit its release. Also IGFs provide feedback regulation and inhibit GHRH and stimulate GHIH
Growth hormone releasing hormone (GHRH)
starvation, protein deficiency
decreased blood glucose or fatty acids
Estrogen & androgens
Stimulate GH secretion
increased blood glucose or blood fatty acids
Growth hormone (-ve feedback)
Inhibit GH secretion
What is panhypopituitarism?
global underactivity of the pituitary gland - under secretion of growth hormone
What are some causes for panhypopituitarism?
pituitary tumors, thrombosis of pituitary vessels, trauma
What is the effect of panhypopituitarism?
lethargy, weight gain, loss of sexual function
Treatment for panhypopituitarism?
What are some causes of dwarfism?
congenital defect, pituitary tumor, trauma causing panhypopituitarism, or just GH deficiency
Effect of dwarfism?
Treatment of dwarfism?
administer human GH, thyroxine, cortisol
GH hypersecretion during childhood.
Cause of gigantism? Effect? Treatment?
hyperactivity of otherwise normal cells, pituitary tumor; rapid growth, hyperglycemia (can lead to Diabetes Mellitus); somatostatin, surgery
Two things that excessive growth (gigantism) can cause?
ketosis; insulin resistance
Over-secretion of GH
Cause of acromegaly?
pituitary tumor AFTER puberty
Effect of acromegaly? Treatment?
bones grow in thickness, kyphosis, enlarged organs, diabetes; somatostatin, surgery
Members of the POMC family are polypeptide hormone products of the (blank) gene. They are generated as a result of cleavage of POMC by (blank)
2 hormones in the POMC family. What is their target? What is their major action?
1. adrenal cortex - increase synth and secretion of adrenal cortical steroids
2. fat - increase fat mobilization
ACTH and β-LPH can be further cleaved into β-endorphins and α-MSH. Under conditions where ACTH levels are increased, α-MSH can be produced and may lead to (blank) of the skin
Six hormones released by the hypothalamus? Which are releasing? Which are inhibitory?
DA - inhibitory
SS - inhibitory
↑ Synthesis & secretion of thyroid-stimulating hormone (TSH) & prolactin (PRL)
thyrotropin-releasing hormone (TRH)
↑ Synthesis & secretion of luteinizing hormone (LH) & follicle-stimulating hormone (FSH)
Gonadotropin-releasing hormone (GnRH)
↑ Synthesis & secretion of adrenocorticotrophic hormone (ACTH)
Corticotropin-releasing hormone (CRH)
↑ Synthesis & secretion of growth hormone (GH)
Growth hormone-releasing hormone (GHRH)
↓ GH secretion
Growth hormone-inhibitory hormone (PHIH; somatostatin)
↓ Synthesis & secretion of prolactin (PRL)
Prolactin-inhibiting hormone (PIH)
Also known as dopamine
What is unique about the hypothalamic hormone dopamine compared to the other five?
it has an amine structure, instead of a peptide structure
Hypothalamic releasing/inhibitory hormones are secreted in the hypothalamus and collect in the (blank); enter the portal system and are conducted to the (blank) where they influence secretion from glandular cells. This is an example of...
median eminence; anterior pituitary
Several hypothalamic hormones are released in a pulsatile fashion but only pulsatile (blank) release is critical for pituitary (gonadotropin) secretion
The pulsatile release of GnRH in pituitary portal blood can be measured in the peripheral blood as (blank)
Hypothalamus is a (blank) for environmental and sensory information
Three types of feedback loops
1. long loop negative feedback
2. short loop negative feedback
3. ultra-short loop negative feedback
CRH secreted from hypothalmus→
ACTH secreted from anterior pituitary→
Cortisol secreted from adrenal cortex;
Cortisol inhibits ACTH release and CRH release.
long loop negative feedback
CRH secreted from hypothalmus→
ACTH secreted from anterior pituitary;
ACTH inhibits CRH release.
short loop negative feedback
Hypothalamic or pituitary hormones directly regulating the cells that secrete the hormone.
CRH secreted from hypothalmus;
THEN CRH inhibits further CRH release.
ultra-short loop negative feedback
Endocrinopathies are classified as primary, secondary, or tertiary
Primary - at level of (blank)
Secondary - at level of (blank)
Tertiary - at level of (blank)
target organ; pituitary; hypothalamus
Hormones of the posterior pituitary are secreted by (blank). The bodies of these neurons are located in the (blank). The hormones are synthesized in the cell bodies and transported down the nerve axons into the posterior pituitary.
Two hormones of the posterior pituitary
Origin of oxytocin: magnocellular neurons in the (blank) nuclei
Half life of oxytocin? Functions?
2 mins; milk ejection, hastens delivery
Origin of ADH: magnocellular neurons in the (blank) nuclei
Half life of ADH? When is it secreted?
2 minutes; in response to low blood volume or increased plasma osmolality
2 functions of ADH
1. reabsorption of water in collecting tubules (V2 receptor --> cAMP --> increased aquaporins)
2. vascular smooth muscle contraction (V1 receptor --> IP3, DAG --> [Ca+])
Two pathophysiologies of ADH secretion
1. diabetes insipidus
Problem: Unable to conserve water due to ↓ADH synthesis (central DI) or insensitivity to ADH at the collecting ducts (nephrogenic DI)
Causes: trauma, tumors, infection (e.g. meningitis)
Principle symptoms: ↑water loss from kidneys (polyuria) triggers ↑ thirst (polydipsia)
Increased water retention, atria of heart stretched, increased ANF, sodium loss, hyponatremia, concentrated urine
ADH secreted from lung cancer
Causes of SIADH
asymptomatic during early stages especially if serum sodium falls slowly. Rapid fall associated with confusion, drowsiness, convulsions, coma and death.
symptoms of SIADH
Damage from malnutrition (e.g. anorexia, bulimia),
Other physical injury to the hypothalamus.
causes of hypothalamic disease
Body temperature regulation,
Sodium and water balance,
effects of hypothalamic disease
Usually benign adenomas
May produce excess hormone or restrict activity of the pituitary to lessen hormone production
pituitary gland tumors
Most common pituitary gland tumor
What causes this?
Polyuria and polydipsia
What causes this?
What causes this?
What causes this?
What causes this?
Failure to thrive, short stature, fatigue, weakness, decreased QOL
Increased prolactin, increased milk production, decreased reproductive function
increased GH, increased bone growth, acromegaly or gigantism
increased ACTH and cortisol
Hormones of the posterior pituitary are not synthesized there, they are stored there, and they are NOT secreted by the pituicytes, but by NEURONS.