Intro to Endocrinology Flashcards
Spring 2024 (104 cards)
1
Q
Hormone
A
Chemical substance that sends a message to another cell in the body
2
Q
Give example of endocrine, exocrine, neurocrine, and paracrine cellular messaging
A
Endocrine: bloodstream
Exocrine: GI tract
Neurocrine: neurologically
Paracrine: interstitial fluid
3
Q
List the glands that we cover
A
- Hypothalamus
- Pituitary
- Thyroid
- Parathyroid
- Adrenal gland
- Pancreas
- Ovaries
- Testes
4
Q
List the 6 hormone classifications
A
- Amine
- Peptide
- Protein
- Glycoprotein
- Steroid
- Fatty acid
5
Q
Amine hormones
A
- Trp or Tyr are modified to create amine hormones
- Epinephrine, triiodothyronine, thyroxine, serotonin
- Very short half-lives
6
Q
Peptide hormones
A
- Chain < 50 aa
- Water soluble, don’t cross membranes easily
- Must first bind to membrane-bound receptors
- Vasopressin and oxytocin
7
Q
Protein hormones
A
- Chain > 50 aa
- ACTH, calcitonin, insulin, glucagon, oxytocin
8
Q
Glycoprotein hormones
A
- Conjugated to carbs
- FSH, LH, and TSH
- Solubility and half-life similar to protein hormones
9
Q
Steroid hormones
A
- Derived from lipid, usually cholesterol
- Hydrophobic, must be transported in blood bound to carrier proteins
- Can cross membranes due to lipids
- Aldosterone, cortisol, estrogen, progesterone, testosterone, other androgens (DHEA)
10
Q
Fatty acid hormones
A
- Derivatives of arachidonic acid
- Eicosanoids, leukotrienes, prostaglandins, thromboxanes
- Rapidly degraded, effective for only seconds
11
Q
Metabolism
A
The sum of chemical processes that occur within a living organism to maintain life (catabolism + anabolism)
12
Q
Anabolism
A
Creating substances
13
Q
Catabolism
A
Breaking down substances
14
Q
Hormone metabolism
A
The speed of anabolism or catabolism determines the extent to which hormones are capable of binding to receptors and eliciting effects
15
Q
Conditions that modify hormone metabolism/levels
A
- Speed of production or breakdown affects blood hormone levels
- Amount of carrier protein affects protein-bound hormone levels
- Disease states (e.g., cirrhosis) affect enzymatic hormone breakdown
16
Q
Effects of alcohol consumption on hormone metabolism
A
- Increase testosterone degradation
- Leads to cirrhosis, which can cause less albumin and other binding proteins
17
Q
Adrenal steroid hormone synthesis
A
Many hormones are produced in the adrenal gland by a cascade of enzymatic reactions
18
Q
Which two organs predominantly eliminate hormones?
A
Kidney and liver
19
Q
General mechanism for hormone elimination
A
Blood -> Liver tags certain hormones for destruction or creation of different substances (or kidney)
20
Q
Steroid hormone elimination mechanism
A
Inactivating metabolic pathways and excretion in urine or bile
21
Q
Thyroid hormone excretion mechanism
A
Inactivated by intracellular deiodinases
22
Q
Catecholamine hormone excretion mechanism
A
Rapidly degraded within blood circulation
23
Q
Fatty acid derivative hormone excretion mechanism
A
Rapidly inactivated by metabolism and typically active for a short time period (seconds)
24
Q
Negative feedback
A
A stimulus will feedback upstream and decrease production of itself (e.g., thyroid)
25
Positive feedback
Increase the stimulus received until a distinct endpoint is achieved (e.g., coagulation cascade)
26
Thyroid negative feedback mechanism
:)
27
Primary endocrine disorder
Thyroid main problem because lack thyroid hormones (T3, T4)
28
Secondary endocrine disorder
Pituitary is the problem. Lack TSH
29
Tertiary endocrine disorder
Hypothalamus is the problem. Lack TRH
30
List factors that affect hormone levels
## Footnote
I would review slide details for these
- emotional stress
- time of day
- menstrual cycle
- menopause
- diet
- drugs
31
List the 3 distinct parts of the pituitary
- anterior pituitary
- intermediate lobe
- posterior pituitary
32
Posterior pituitary
- Arises from diencephalon
- Responsible for storage/release of oxytocin and AVP/ADH
33
Anterior pituitary
Receives 80%-90% of blood supply and many hypothalamic factors via the hypothalamic-hypophyseal portal system
34
When can pituitary function be gestationally detected?
Between 7th and 9th week
35
Lactotrophs
Prolactin-secreting cells
36
Somatotrophs
GH-secreting cells
37
Thyrotrophs
TSH-secreting cells
38
Corticotrophs
ACTH-secreting cells
39
Gonadotrophs
LH- and FSH-secreting cells
40
Afferent pathways (inputs) to the hypothalamus
Integrated in various specialized nuclei and then resolved into specific responses
41
Relate the hypothalamus' many efferent (output) neural connections to higher brain centers to responses for each specific pituitary hormone
The responses are similar for each hormone and characterized by negative feedback mechanisms, pulsatility, and diurnal variation
42
Give example of endocrine feedback loop
Hypothalamic-pituitary-thyroidal axis
Thyroid secretes thyroxine to act on hypothalamus
43
How are all anterior pituitary hormones secreted? Examples?
Pulsatile fashion, such as LH and FSH
44
How is pulse frequency of secretion regulated?
Neural modulation and is specific for each hypothalamus-pituitary-end organ unit
45
Which hormone's secretion profile does GnRH pulse frequency affect?
LH
46
Hormones with diurnal variation
- ACTH (trough 11pm-3am, peak 6am-9am
- TSH nocturnal levels 2x daytime levels
47
**T/F**
According to autopsy studies, up to **50%** of people harbor clinically silent pituitary adenomas
False, 20%
48
**T/F**
Pituitary tumors are found in **10-30%** of normal individuals undergoing MRI exams
True
49
**T/F**
Pituitary tumors account for **78%** of lesions from patients who have undergone transsphenoidal surgery
False, 91%
50
When can pituitary enlargement be seen?
Puberty and pregnancy
51
List tumors in order of clinical significance
1. Prolactin-secreting
2. "null cell"
3. TSH, GH, ACTH, or gonadotropin-secreting
52
List anterior pituitary hormones plus functions
- GH = tissue growth
- TSH = thyroid hormones
- ACTH = cortical hormones
- FSH = testes/ovaries
- LH = testes/ovaries
- PRL (prolactin) = breast glandular tissue
53
List posterior pituitary hormones
- oxytocin = uterine contraction/lactation
- ADH/AVP/vasopressin = kidney water reabsorption
54
Compare hormones secreted from anterior pituitary (AP) to those secreted from hypothalamus
- AP hormones are larger and more complex
- May be tropic or direct effectors
55
Tropic hormones
Actions are specific for another endocrine gland
56
Direct effectors
Directly act on peripheral tissue
57
Hypothalamic-pituitary target organ axis
:)
58
Role of pituitary gland and why
Vital for normal growth because it secretes **somatotropin** aka **growth hormone**
59
Effect or removing the pituitary
**Growth ceases**
Also ceases if hormonal products from other endocrine glands acted on by anterior pituitary are replaced
60
How do you restore growth?
Administer GH
61
Somatotropin
Same as growth hormone, which is pulsatile
62
Why is GH amphibolic?
Bc it directly influences both anabolic and catabolic processes
63
How does GH affect fasting/fast states?
- Allows person to transition from fed to fasting state
- No shortage of normal intracellular oxidation substrates
64
How does GH affect insulin/glucose metabolism?
- Inhibits insulin effects
- Promotes hepatic gluconeogenesis and lipolysis
- Lipolysis enhanced by providing oxidative substrates for peripheral tissue *and* conserves glucose for CNS by stimulating hepatic delivery of glucose/inhibiting insulin-mediated glucose metabolism
65
Is GH a tropic hormone or direct effector?
Direct effector on many peripheral tissues
66
Insulin-like growth factor (IGF)
- Growth factor induced by GH in liver
- Cell surface receptors distinct from insulin, but IGF-2 can cross-react with insulin receptor and cause hypoglycemia
- Mediates indirect effects of GH
67
**T/F**
Single random GH measurement is diagnostic
False, it's rarely diagnostic
GH measurement has limited value
68
GH testing
- Baseline measurements helpful
- Interpret in conjunction with glucose suppression tests to diagnose acromegaly
- Interpret in conjunction with GH stimulation test to diagnose GH deficiency
69
How to diagnose acromegaly in childhood/adolescence
- Glucose tolerance test and measuring IGF-1 (preferred)
- IGF-1 useful in eval excess/deficient growth disorders in both adults and children
- IGF-1 can monitor recombinant GH treatment and follow-up
70
Strategies to stimulate GH
- Insulin-induced hypoglycemia (outdated)
- Combo infusions of GHRH and L-arginine
- Infusion of L-arginine coupled with oral L-DOPA
71
Acromegaly
- Pathologic or autonomous GH excess, usually result of tumor
- If GH-producing tumor occurs before epiphyseal closure of long bones, then **gigantism** results
72
What happens if GH-producing tumor happens after puberty?
- Classical/insidious features: bony and soft tissue overgrowth
- Progressive enlargement of hands and feet, growth of facial bones (mandible/skull), teeth gaps, arthritis, sleep apnea, excess sweating/heat intolerance
73
Acromegaly treatment
- Tumor ablation with continued function of remaining pituitary
- Transsphenoidal adenctomy procedure of choice
- External beam/focused irrradiation may take several years to take full effect
- Treatment does NOT reverse bone growth effects
74
How does GH deficiency manifest in children
Growth failure
Not all short pts have GH deficiency
75
How does GH deficiency manifest in adults?
- Complete or partial anterior pituitary failure
- Vague symptoms: social withdrawal, fatigue, loss of motivation, diminished feeling of well-being
- Osteoporosis and body composition alterations
76
Prolactin
- Structurally related to GH and human placental lactogen
- Stress hormone
- Vital functions in reproduction
- Unique due to **tonic inhibition** as mode of hypothalamic regulation instead of intermittent stimulation
77
Prolactinoma
- Pituitary tumor that secretes prolactin, most common functional pituitary tumor
- Clinical presentation depends on pt age/gender, tumor size
78
Prolactin-inhibitor factor
Dopamine
Only neuroendocrine signal that inhibits prolactin
79
Management of prolactinoma
- Reducing tumor mass
- Restoring normal gonadal function/fertility
- Preventing osteoporosis
- Preserving normal anterior/posterior pituitary function
- Therapeutic options: simple observation, surgery, radiotherapy, medical management with dopamine agonists
80
Prolactin > 150ng/mL indicates what cause?
- Prolactinoma
- Degree of elevation correlates with tumor size
81
Prolactin 25-100 ng/mL indicates what causes?
- Pituitary stalk interruption
- Dopaminergic antagonist meds
- Primary thryoidal failure
- Renal failure
- Polycystic ovary syndrome
82
Clinical eval of hyperprolactinemia
- History/physical exam usually enough to exclude most common non-endocrine causes
- Essential to obtain **TSH** and **free T4** to eliminate primary hypothyroidism as a cause for the elevated prolactin
- If pituitary tumor sus, assess other anterior pituitary function: ACTH/cortisol, LH, FSH, gender-specific gonadal steroids, MRI
83
Idiopathic galactorrhea
- Lactation in women with normal prolactin levels
- Usually seen in women who have gotten pregnant several times and no pathological implication
84
Hyperprolactinemia associated with...?
- Renal failure
- Cirrhosis
- Hypothyroidism
- Trauma
- Inflammation
- Drugs (TCS, phenothiazine's, reserpine)
- Adrenal insufficiency
- Prolactinoma
85
Clinical manifestation of prolactinoma in non-postpartum women and women with amenorrhea
- Galactorrhea 30-%0&
- Menstrual irregularity
- Infertility
86
Clinical manifestation of prolactinoma in men
- Hypogonadism
- Erectile dysfunction
- Galactorrhea < 30%
- Visual abnormalities
- Extra-ocular muscle weakness
- Headache
87
Panhypopituitarism
Complete loss of anterior pituitary function due to failure of either pituitary or hypothalamus
88
Monotropic hormone deficiency
Loss of single pituitary hormone
89
Lab diagnosis of hypopituitarism
- Straight-forward
- **Primary failure** of endocrine gland accompanied by dramatic **increases** in circulating levels of corresponding pituitary tropic hormone
- **Secondary failure** (hypopituitarism) associated with **low or normal** levels of tropic hormone
90
Etiology of hypopituitarism
- Various types of tumors
- Postpartum ischemic necrosis of pituitary
- Infiltrative diseases such as hemochromatosis, sarcoidosis, histiocytosis
- Fungal infections, TB, syphilis
- Lymphocytic hypophysitis
- Severe head trauma, pituitary surgery, radiotherapy
91
Panhypopituitarism treatment
- Thyroxine, glucocorticoids, gender-specific sex steroids
- Replacement therapy tricker in patients who desire fertility
92
Posterior pituitary
Extension of forebrain and represents the storage region for AVP and oxytocin
93
Where are AVP and oxytocin synthesized?
- Supraoptic and paraventricular nuclei of the hypothalamus and transported to the neurohypophysis via axons in the hypothalamoneurohypophyseal tract
- Also made outside of hypothalamus in various tissues
94
Synthesis of AVP and oxytocin tightly linked to production of ______
Neurophysin
95
Oxytocin
- Critical role in lactation, labor, and parturition (childbirth)
- Secretion responds to **positive** feedback loop
- Uterine contractions propagate oxytocin release, causing more contractions
- Maternal nurturing and mother-infant bonding
- Effects on pituitary, renal, cardiac, metabolic, and immune function
96
Pitocin
Synthetic oxytocin
97
AVP major action
Regulate renal free water excretion
98
Where are vasopressin receptors in kidney concentrated?
Renal collecting tubules and ascending limb of loop of Henle
99
Other AVP functions
- Potent pressor agent (elevates BP)
- Affects blood clotting by promoting Factor VII release from hepatocytes
- Von willebrand factor release from endothelium
100
How dos plasma osmolality increase affect AVP secretion?
Increases vasopressin secretion
Osmoreceptors very sensitive to even small changes
101
What happens to AVP release if blood pressure or volume fall?
Vascular baroreceptors initiate AVP release
102
How is AVP regulated?
By hypothalamic osmoreceptors and vascular baroreceptors
103
Diabetes insipidus
AVP deficiency or resistance
104
AVP excess
- Much more difficult to treat than deficiency due to free water retention
- Restricting free water intake to small amounts each day has been main treatment
