M4.2-PITUITARY AND HYPOTHALAMUS TRANS Flashcards
1
Q
What is the pituitary gland’s weight and size?
A
0.6 grams 12mm transverse 8mm anteroposterior diameter123
2
Q
What does “hypophysis” mean?
A
Undergrowth (Greek origin)423
3
Q
Why was it historically called “spit mucus” gland?
A
Ancient belief it secreted nasal mucus (later disproved)423
4
Q
What makes it the “master gland”?
A
Secretes hormones regulating thyroid adrenal gonadal function567
5
Q
When does pituitary function begin in gestation?
A
7th-9th week4[^4]3
6
Q
What bone houses the pituitary gland?
A
Sphenoid’s sella turcica (Turkish saddle)163
7
Q
What membrane surrounds the gland?
A
Dura mater163
8
Q
What connects the hypothalamus to the pituitary?
A
Infundibulum/pituitary stalk163
9
Q
What embryonic structure forms the anterior pituitary?
A
Rathke’s pouch1[^4]3
10
Q
How does it receive hypothalamic signals?
A
Hypophyseal portal system (80-90% blood supply)413
11
Q
What are the 5 cell types and their hormones?
A
Somatotrophs (GH) Lactotrophs (PRL) Thyrotrophs (TSH) Gonadotrophs (FSH/LH) Corticotrophs (POMC)457
12
Q
What hormones derive from POMC?
A
ACTH β-endorphin β-lipotropin473
13
Q
How developed is the human pars intermedia?
A
Poorly developed (often cystic)413
14
Q
What hormones does the posterior pituitary store?
A
Oxytocin ADH (synthesized in hypothalamic nuclei)163
15
Q
Where are ADH/oxytocin produced?
A
Supraoptic and paraventricular nuclei163
16
Q
What is the posterior pituitary’s embryonic origin?
A
Diencephalon (neural tissue)413
17
Q
What two broad categories classify pituitary dysfunction?
A
Hormonal excess (adenomas) deficiency (trauma/tumors)416
18
Q
How does the hypophyseal portal system work?
A
Hypothalamic hormones → portal veins → anterior pituitary targets1[^4]3
19
Q
What feedback system regulates hormone release?
A
Hypothalamic-pituitary-target organ axis (negative feedback)467
20
Q
What visual defect suggests pituitary tumor?
A
Bitemporal hemianopia (optic chiasm compression)163
21
Q
How are pituitary adenomas surgically treated?
A
Trans-sphenoidal approach via sphenoid sinus163
22
Q
What distinguishes functional vs non-functional adenomas?
A
Hormone hypersecretion vs mass effect symptoms163
23
Q
What is the relational anatomy of the hypothalamus-pituitary unit?
A
Hypothalamus connects to pituitary via infundibulum; anterior lobe (adenohypophysis) develops from Rathke’s pouch; posterior lobe (neurohypophysis) from diencephalon123
24
Q
What are the functional aspects of the hypothalamic-hypophyseal unit?
A
Feedback mechanisms
25
What defines hormonal pulsatility?
Rhythmic/episodic secretion (e.g.
26
What is a zeitgeber in hormonal cyclicity?
External cues synchronizing internal clocks (e.g.
27
What are the three feedback loops in the hypothalamic-pituitary-thyroid axis?
Short (thyroid→pituitary)
28
Which hypothalamic hormones have multiple actions?
TRH (stimulates TSH/prolactin)
29
Where are hypophysiotropic hormones found?
CNS
30
What are the two types of anterior pituitary hormones?
Direct effectors (e.g.
31
How does GH function as a direct effector?
Stimulates liver growth factors and substrate metabolism423
32
What is the role of tropic hormones?
Direct endocrine glands (e.g.
33
What regulates anterior pituitary hormone release?
Hypothalamic releasing/inhibiting hormones via hypophyseal portal system153
34
How do hypothalamic neurons communicate with the posterior pituitary?
Axonal transport of oxytocin/ADH from supraoptic/paraventricular nuclei153
35
What clinical defect occurs with optic chiasm compression?
Bitemporal hemianopia (pituitary tumor complication)156
36
What percentage of people have silent pituitary adenomas in autopsy studies?
Up to 20%[^UserNotes]12
37
What MRI finding is seen in normal individuals regarding pituitary tumors?
10-30% show incidental pituitary lesions[^UserNotes]12
38
What percentage of transsphenoidal surgery cases involve pituitary tumors?
91%[^UserNotes]3
39
When does physiologic pituitary enlargement occur?
During puberty and pregnancy[^UserNotes]3
40
What is the most common type of pituitary tumor?
Prolactin-secreting tumors[^UserNotes]45
41
What defines null cell pituitary adenomas?
Absence of anterior pituitary cell differentiation[^UserNotes]3
42
What hormonal subtypes do pituitary tumors secrete?
GH gonadotropins ACTH TSH[^UserNotes]3
43
What defines atypical pituitary tumors?
MIB-1 >3% excessive p53 increased mitotic activity[^UserNotes]3
44
What size defines pituitary macroadenomas?
≥1 cm diameter[^UserNotes]35
45
What size defines pituitary microadenomas?
<1 cm diameter[^UserNotes]35
46
What is the most abundant pituitary hormone?
Growth hormone (somatotropin)[^UserNotes]3
47
Which cells produce growth hormone?
Somatotrophs[^UserNotes]3
48
What stimulates GH secretion?
GHRH and ghrelin[^UserNotes]3
49
What inhibits GH secretion?
Somatostatin[^UserNotes]3
50
When does GH secretion peak?
At sleep onset[^UserNotes]3
51
What suppresses GH secretion?
75g glucose load[^UserNotes]3
52
What metabolic effects does GH have?
Antagonizes insulin stimulates gluconeogenesis/lipolysis (hyperglycemic)[^UserNotes]3
53
What condition results from GH deficiency in children?
Hypoglycemia[^UserNotes]3
54
What is the major GH-induced growth factor?
IGF-1 (somatomedin C)[^UserNotes]3
55
What causes acromegaly?
Pathologic GH excess (usually pituitary tumor)[^UserNotes]35
56
What is gigantism?
GH excess before epiphyseal closure[^UserNotes]35
57
What are acromegaly's physical features?
Enlarged hands/feet/jaw skull thickening[^UserNotes]35
58
What metabolic complications occur in acromegaly?
Diabetes hypertension atherosclerosis[^UserNotes]35
59
What diagnostic test screens for GH excess?
IGF-1 level[^UserNotes]35
60
What confirms GH excess diagnosis?
75g OGTT failure to suppress GH <1 ng/mL[^UserNotes]35
61
What is first-line treatment for GH-secreting tumors?
Transsphenoidal adenomectomy[^UserNotes]35
62
What medications treat GH excess?
Somatostatin analogs (octreotide) GH receptor antagonists (pegvisomant)[^UserNotes]35
63
When are dopamine agonists effective for GH tumors?
If they co-secrete prolactin[^UserNotes]35
64
What rare condition occurs if tumors co-secrete TSH?
Hyperthyroidism[^UserNotes]3
65
How does hyperthyroidism from pituitary tumors affect lifespan?
Shortens life expectancy due to cardiovascular risks[^UserNotes]3
66
What populations does growth hormone deficiency (GHD) affect?
Children (familial/tumor-related) and adults (pituitary abnormalities)123
67
What causes pediatric GHD?
Genetic defects (GHRH/GH gene mutations)
68
What causes adult GHD?
Structural/functional pituitary abnormalities (often acquired)123
69
What is the primary symptom of childhood GHD?
Growth failure (<2 inches/year) with normal body proportions145
70
What physical features may accompany childhood GHD?
Chubby build
71
What are adult GHD symptoms?
Osteoporosis
72
What is the gold standard diagnostic test for GHD?
Insulin tolerance test (measures GH response to hypoglycemia)11
73
What is the screening test for GHD?
Physical activity/exercise test (measures GH elevation post-exercise)11
74
What GH threshold confirms GHD during stimulation tests?
<5 ng/mL (adults) or <10 ng/mL (children)11
75
What is the treatment for GHD?
GH replacement therapy (daily/weekly injections)147
76
What are normal GH reference ranges?
Males: 0.01-1.0 ng/mL; Females: 0.01-3.5 ng/mL11
77
What hormone inhibits prolactin secretion?
Dopamine (prolactin inhibitory factor)11
78
What is the most common functional pituitary tumor?
Prolactinoma (prolactin-secreting)11
79
What are premenopausal symptoms of prolactinoma?
Menstrual irregularity
80
What are male/postmenopausal prolactinoma symptoms?
Headaches
81
What medications cause hyperprolactinemia?
Antipsychotics (phenothiazines)
82
How does pituitary stalk disruption cause hyperprolactinemia?
Blocks dopamine transport → loss of prolactin inhibition11
83
What endocrine conditions elevate prolactin?
Chronic kidney disease (reduced clearance) and PCOS (high estrogen)11
84
What is the consequence of chronic hyperprolactinemia?
Hypogonadism (low estrogen/testosterone → infertility)11
85
What physiologic factors increase prolactin?
Breast stimulation
86
What is the first step in evaluating hyperprolactinemia?
Careful history/physical to exclude nonendocrine causes (e.g.
87
Why check TSH/free T4 in hyperprolactinemia?
To rule out primary hypothyroidism (low T4/high TSH → elevated TRH → stimulates prolactin)412
88
What imaging is preferred for suspected pituitary tumors?
MRI of the sella turcica (detects microadenomas/macroadenomas)156
89
What are normal prolactin reference ranges?
Males: 4.0-15.2 ng/mL; Females: 4.8-23.3 ng/mL437
90
What prolactin level suggests macroprolactinoma?
>500 ng/mL (diagnostic)567
91
What are therapeutic goals for prolactinoma?
Reduce tumor mass
92
How does hyperprolactinemia cause osteoporosis?
Increased urinary calcium excretion → hypocalcemia → impaired bone mineralization483
93
What is first-line treatment for prolactinoma?
Dopamine agonists (cabergoline/bromocriptine)127
94
When is surgery indicated for prolactinoma?
Drug resistance
95
What defines idiopathic galactorrhea?
Lactation with normal prolactin levels (nonhormonal cause)483
96
What is panhypopituitarism?
Complete loss of anterior pituitary function44
97
What causes monotropic hormone deficiency?
Isolated loss of one hormone (e.g.
98
What is the most common cause of hypopituitarism?
Pituitary tumors (compression/stalk disruption)44
99
How do parapituitary tumors affect function?
Compress hypothalamus/pituitary stalk (e.g.
100
What causes Sheehan’s syndrome?
Postpartum pituitary infarction (ischemic necrosis)44
101
Which infection causes hypopituitarism?
Tuberculosis/syphilis (rare)44
102
How does hemochromatosis damage the pituitary?
Iron deposition in pituitary/hypothalamus44
103
What autoimmune condition affects the pituitary?
Lymphocytic hypophysitis (linked to ipilimumab)44
104
What genetic disorder causes hypogonadotropic hypogonadism?
Kallmann syndrome (GnRH deficiency)44
105
How is panhypopituitarism treated?
Thyroxine + glucocorticoids + sex steroids44
106
What treatment exists for Kallmann syndrome?
GnRH infusions (restores LH/FSH/testosterone)44
107
Why exclude macroprolactinemia in hyperprolactinemia?
Inactive prolactin isoforms cause false elevations (use PEG precipitation)563
108
What is the "hook effect"?
Artificially low prolactin readings in macroprolactinomas (requires serial dilution)563
109
When is pregnancy testing mandatory in hyperprolactinemia?
All reproductive-age females (physiologic cause)583
110
What dynamic tests help diagnose prolactinomas?
TRH/metoclopramide tests (low specificity; rarely used)564
111
What are the six major anterior pituitary hormones?
TSH LH FSH ACTH GH Prolactin123
112
What is the function of thyroid-stimulating hormone (TSH)?
Stimulates thyroid hormone production (thyroxine)123
113
What do LH and FSH regulate?
Reproductive function (ovulation
114
What is the role of adrenocorticotropic hormone (ACTH)?
Stimulates adrenal cortisol production (stress response)124
115
What is the structural relationship between oxytocin and vasopressin?
Both cyclic nonapeptides with disulfide bridges; differ by 2 amino acids567
116
Where are posterior pituitary hormones synthesized?
Hypothalamic nuclei (supraoptic/paraventricular)67
117
What is oxytocin's primary function?
Uterine contractions during labor and milk ejection567
118
What triggers oxytocin release during labor?
Positive feedback loop (stretching of cervix)567
119
What synthetic form of oxytocin is used medically?
Pitocin (induces labor)55
120
What is vasopressin's primary action?
Water reabsorption in kidneys via aquaporin-2567
121
How does vasopressin respond to plasma osmolality?
Increased osmolality → enhanced secretion567
122
What clotting factors does vasopressin affect?
Factor VII and von Willebrand factor release55
123
What condition results from vasopressin deficiency?
Diabetes insipidus (polyuria/polydipsia)567
124
What receptors regulate vasopressin release?
Hypothalamic osmoreceptors and vascular baroreceptors567
125
What is the structural feature of anterior pituitary hormones?
Peptides (GH
126
How does GH differ from other anterior pituitary hormones?
Directly targets liver/organs (non-tropic)184
127
What is unique about prolactin regulation?
Primarily inhibited by dopamine (no hypothalamic releasing hormone)234
128
What is the hypothalamic-pituitary axis for ACTH?
CRH → ACTH → cortisol (HPA axis)147
129
Why are LH/FSH called gonadotropins?
Target gonads (testes/ovaries)123
130
What is the functional difference between anterior/posterior pituitary?
Anterior produces hormones; posterior stores hypothalamic hormones
