ENDO II - Pituitary Hormones Flashcards
1
Q
what is the anterior pituitary gland made of
A
a true endocrine gland with endocrine cells
2
Q
what is the posterior pituitary made of
A
axon terminals of hypothalamic neurons containing neurons and synaptic terminals
3
Q
where is the pituitary gland located
A
in the sella turcica ventral to the diaphragma sella
4
Q
what hormones do they anterior and posterior pituitary secrete?
A
-anterior: GH, ACTH, TSH, FSH,LH, prolactin
-posterior: ADH/vasopressin, oxytocin
5
Q
what do adenomas cause in children and adults and what cells are involved
A
involves somatotropic cells, causes gigantism in children before closure of long bones epiphyseal plate or acromegaly in adults
6
Q
what cells secrete GH
A
somatotrophs
7
Q
what cells secrete ACTH
A
corticotrophs
8
Q
what cells secrete TSH
A
thyrotrophs
9
Q
what cells secrete LH and FSH
A
gonadotrophs
10
Q
what cells secrete prolactin
A
mammotrophs
11
Q
what is the order of most secreted to least secreted hormones in the anterior pituitary
A
GH > ACTH > TSH > LH AND FSH > prolactin
12
Q
where are hypothalamic hormones released into
A
the primary capillary plexus in the median eminence
13
Q
what do the blood vessels in the hypothalamic-hypophyseal portal carry hypothalamic hormones to
A
sinuses of the anterior pituitary gland
14
Q
what does the hypothalamic-hypophyseal portal system connect
A
hypothalamus to anterior pituitary
15
Q
what is the effect of TRH and what does it act on
A
activating, TSH
16
Q
what is the effect of GnRH and what does it act on
A
activator, LH and FSH
17
Q
what effect does CRH have and on what
A
activating, ACTH
18
Q
what is the effect of GHIH and on what
A
inhibiting, GH
19
Q
what is the effect of GHRH and on what
A
activating, GH
20
Q
what is the effect of PIH and on what
A
inhibiting, Prolactin
21
Q
what is the effect of PRH and on what
A
activating, prolactin
22
Q
how do hypothalamic regulatory hormones signal anterior pituitary cells
A
the hormones bind to GPCRs then through generation of second messengers they either stimulate or inhibit AP hormone secretion
23
Q
what second messengers do hypothalamus and anterior pituitary signaling
A
cAMP via adenylate cyclase and IP3 and DAG via phospholipase C
24
Q
what does GH act on
A
target tissues and as a tropic hormone to the liver which releases IGF1
25
what is the normal concentration of GH in adults and children
1.6-3 ng/ml and higher in children
26
what happens to GH during starvation
increases
27
what does IGF1 act back on in a long negative feedback loop
hypothalamus and anterior pituitary
28
what does GH act back on in a short negative feedback loop
hypothalamus
29
what factors activate GHRH and inhibit SS
sleep, hypoglycemia and stress
30
what factors inhibit GHRH and stimulate SS
aging, disease, glucose
31
how does GH and IGF1 act in the skeleton
increases AA uptake, increases protein synthesis, necessary for linear growth
32
how does GH and IGF1 act on mucscle
increased protein synthesis
33
when is growth hormone highest and lowest
highest a few hours after sleep and during strenuous exercise and lowest during the day
34
what is GH stimulated by
fasting (hypoglycemia), starvation (protein deficiency), stress, exercise and excitement
35
when are the highest and lowest levels of GH throughout our lifetime
high during neonatal period but decreases in childhood, peak in puberty and then declines with age
36
what hormones stimulate GH release
GHRH, dopamine, catecholamines, excitatory amino acids, thyroid hormone
37
what hormones inhibit GH release
somatostatin
IGF1
high glucose
high FFA
38
many of the growth and metabolic effects of GH are mainly produced by ____
IGFs
39
how does IGF act on neighboring cells
in a paracrine manner
40
what is the major site of IGF1 synthesis
liver
41
what happens in osteocyte derived IGF1 in mechanotransduction between osteocytes and osteoblasts
osteocyte responds to mechanical sensors that releases IGF-1 which binds to the osteoblast resulting in bone formation
42
what is the mechanism of action of GH and IGF1
-growth in nearly all tissues in the body ( increased size of cells, mitosis, and differentiation of bone and muscle cells) via IGF1. increased organ size, increased organ function, increased linear growth
-AA uptake and protein synthesis in most cells
- reduced glucose utilization- decreased uptake, increased hepatic glucose production and increased insulin secretion
- mobilization of fatty acids from adipose tissue resulting in increase in FFA in blood and use of FFA for energy
43
what do GH and IGF1 do before fusion of the epiphyseal plates
stimulate chondrogenesis and widening of the epiphyseal plates followed by bone matrix deposition stimulating linear growth
44
what do GH and IGF1 do in adults
regulate normal physiology of bone formation by increasing bone turnover via activation of osteoblasts and also increasing bone resorption via activation of osteoclasts
45
how does GH contribute to insulin resistance
GH decreases uptake of glucose, increasing blood glucose, leading to insulin resistance
46
what does an MRI show in acromegalic patients
a pituitary tumor in 90%
47
what are the features of growth hormone excess in adults
-coarse facial features, large fleshy nose, frontal bossing, jaw malocclusion
-somatotropic adenoma of pituitary
-coronary heart disease
-barrel chest
-DM
-kyphosis
-increased size of hands and feet
- arthritis
-paresthesias
-hyperhidrosis and oily skin
- enlarged frontal sinuses and pituitary fossa
48
what is the treatment for a pituitary microadenoma
surgical resection of the tumor via transphenoidal approach followed by medication GHIH receptor ligand or GH receptor antagonist
49
what is another name for GHIH
somatostatin
50
what are oral manifestation of GH excess
-thick rubbery skin, enlarged nose and thick lips
-macrocephaly
-macrognathia
- mandibular prognathism
- diastemata
- anterior open bite and malocclusion
- macroglossia, dyspnea, dysphagia, dysphonia, sialorrhea
-hypertrophy of pharyngeal and laryngeal tissues -> sleep apnea
51
what are the causes of GH deficiency
-hypothalamic disorders
- mutations: GHRH receptor, GH gene, GH receptor, IGF1 receptor
-combined pituitary hormone deficiencies
- radiation
-psychosocial deprivation
52
what are the clinical manifestations of GH deficiency
-slow linear growth rates
-normal skeletal proportions
-pudgy youthful appearance (decreased lipolysis)
-in the setting of cortisol deficiency -> hypoglycemia
53
what do clinical manifestationf of GH deficiency depend on
time and onset and severity of hormone deficiency
54
what is the most common form of dwarfism
achondroplasia
55
what type of inheritence pattern in achrondroplasia
autosomal dominant
56
what causes achondroplasia
a mutation of FGF3 receptor in cartilage and brain that makes the receptor overly active and inhibits cartilage growth at growth plates so limb growth is reduced
57
what are oral manifestations of GH deficiency
-disproportionate delayed growth of the skull and facial skeleton -> small facial appearance
-tooth formation and growth of the alveolar regions of the jaws abnormal and may be disproportionately smaller than adjacent anatomic structures
-solitary median maxillary central incisor
- eruption of primary and secondary dentition and shedding of deciduous teeth are delayed
58
how are tooth formation and growth of the alveolar regions of jaws abnormal in GH deficiency
-tooth crowding and malocculsion
-a high tendency for plaque accumulation
-difficulty maintaining good oral hygiene
- prone to gingivitis and periodontal disease
59
what dentition is solitary median maxillary central incisor seen in with GH deficiency
both primary and permanent
60
how are oral manifestations of GH deficiency managed
correct dental and skeletal malocclusions
61
what does the posterior pituitary contain
100,000 unmyelinated axons of neurons whose cell bodies are in the hypothalamus- paraventricular nucleus and supraoptic nucleus
62
what does the posterior pituitary secrete
ADH/vasopressin and oxytocin
63
how many amino acids make up the posterior pituitary hormones
9
64
does each nucleus in the posterior pituitary only secrete one hormone
predominately one neurohormone but it can synthesize and secrete some of the other
65
what hormone does the paraventricular nucleus secrete
oxytocin
66
what hormone does the supraoptic nucleus secrete
ADH
67
what does ADH do in blood vessels
contraction of vascular smooth muscle via V1 receptors
68
what does ADH do in renal tubules
-binds to V2 receptors in the late distal tubule and collecting duct
-aquaporin 2 proteins are then inserted into the apical membrane of tubular epithelial cells, allowing for water reabsorption (and AQP-3 and AQP-4 on the basolateral membrane)
69
what are the stimuli for ADH secretion
-decreased blood volume
- increased osmolarity
-decreased blood pressure
70
what is hypodipsia and what does it result in
decreased or absent feeling of thirst which results in reduced intake of water and can cause hypernatremia
71
what can hypodipsia trigger
osmolarity change that would stimulate ADH secretion by posterior pituitary
72
when is hypodipsia seen
in eldery people, lesions in hypothalamus, head trauma,hydrocephalus or subarachnoid hemorrhage
73
what levels of ADH are associated with diabetes insipidus? syndrome of inappropriate ADH?
-DI: decreased ADH
-SIADH: increased ADH
74
what is diabetes insipidus due to
insufficient production or lack of kidney response to ADH
75
what does diabetes insipidus present as
polyuria
76
what is polyuria
excretion of large volumes of urine that is hypotonic and tasteless
77
what is a diagnositic test of diabetes insipidus
dehydration test
78
what are the other causes of polyuria
-primary ingestion of excess fluid : primary polydispia
- increased metabolism of ADH (pregnancy)
79
what is SIADH
increased and uncontrolled secretion of ADH that causes volume expansion and hyponatremia
80
what causes SIADH
surgery, pain, stress
81
what does oxytocin do
-stimulates contraction of the uterus towards the end of gestation
- causes milk ejection from the breasts in lactation
82
what does prolactin do
causes milk production
83
describe the relationship between prolactin and oxytocin
permissive
84
what is a sign and give example
objective evidence of disease that can be seen or measured
ex: polyuria, tachycardia
85
what is a symptom and give example
cannot be measured, they are subjective and reported by the person
ex: headache, numbness
