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ENDOREPRO MODULE > Hyper/Hypo Calcemia Plus General Physiology > Flashcards

Hyper/Hypo Calcemia Plus General Physiology Flashcards

0
Q

Describe the normal equilibrium balance between serum ionized Ca and PTH production by the parathyroid gland?

A

A small decrement in serum ionized calcium will STIMULATE PTH release.
A small increment in serum ionized calcium will SUPPRESS PTH release.

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1
Q

What is the dominant hormonal control of serum Calcium?

A

PTH

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2
Q

What are the three direct effects of PTH release on Ca homeostasis?

A

Stimulate osteoclast-mediated release of Ca from bone.
Decrease renal Ca clearance
Stimulate renal 1-alpha hydroxylase to convert calcidiol to calcitriol.

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3
Q

More calcitriol in the system leads to what physiologic phenomenon?

A

Enhances gut absorption of Ca

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4
Q

PTH secretion is STIMULATED by an elevated or decline in serum phosphate?

A

Elevated serum phosphate

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5
Q

What is the phosphaturic effect?

A

PTH directly reduces the renal tubular reabsorption of phosphate from glomerular filtrate.

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6
Q

Place Vitamin D, calcitriol and calcidiol in order of potency.

A

Calcitriol&raquo_space; calcidiol > Vitamin D.

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7
Q

What is the prominent influence of the Vitamin D group (calciferols) of steroid hormones?

A

Promote gut absorption of BOTH calcium and phosphate.

Leads to an increase SERUM level of both.

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8
Q

What cells produce calcitonin?

A

C-cells of the thyroid

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9
Q

What is the function of calcitonin?

A

Opposed the PTH effect on bone -> promotes uptake of calcium by bone.
Calcitonin also promotes renal calcium excretion.

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10
Q

What are the thyroid hormones?

A

thyroxine and triiodothyronine

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11
Q

What are the three forms of Calcium in serum?

A

Protein bound.
Ionized.
Complexed (bound weakly to bicarbonate, HPO4, citrate, or lactate.

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12
Q

What is the precursor molecule for all steroid hormones?

A

Derived from cholesterol

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13
Q

Can steroid hormones be stored within intracellular vesicles?

A

No. Steroid hormones can diffuse freely through lipid membranes and cannot be stored within intracellular vesicles. Because of this they are produced continually.

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14
Q

Since steroid hormones are lipid soluble, they must circulate bound to what?

A

Plasma proteins.

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15
Q

T/F Steroid hormones are freely filtered by the kidney.

A

FALSE. They are protein-bound. They have a long half-life relative to most peptide hormones.

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16
Q

Where are steroid hormones primarily metabolized?

A

By the liver.

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17
Q

What are the sex steroids?

A

Testosterone, progesterone, estrogen.

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18
Q

What are the adrenal steroids?

A

Cortisol

Aldosterone.

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19
Q

What is the precursor molecule for the thyroid hormones?

A

Thyroid hormones are derived from amino acid TYROSINE rather than cholesterol

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20
Q

What are the six hypothalamic hormones?

A 
CRH
GnRH
TRH
GHRH
Somatostatin
Dopamine
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21
Q

What is the physiologic action of CRH?

A

Stimulates ACTH secretion from the anterior pituitary.

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22
Q

What does ACTH stand for?

A

adrenocorticotropin hormone

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23
Q

What is the physiologic action of GnRH?

A

Stimulates gonadotropin secretion from anterior pituitary.

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24
What is the physiologic action of TRH?
Stimulates TSH secretion from anterior pituitary.
25
What does TRH stand for?
Thyrotropin releasing hormone
26
Physiologic action of GHRH?
Stimulates growth hormone secretion from anterior pituitary
27
Somatostatin physiologic action?
Inhibits GH secretion from anterior pituitary.
28
Dopamine physiologic action in terms of endocrinology?
Inhibits prolactin secretion from anterior pituitary.
29
Name the 6 anterior pituitary hormones?
``` FSH LH ACTH TSH Prolactin GH ```
30
ACTH physiologic action?
Stimulates glucocorticoid and androgen synthesis in the adrenal cortex.
31
TSH physiologic actions?
Stimulates thyroid hormone synthesis in thyroid gland.
32
LH physiologic action?
Stimulates testosterone secretion by Leydig cells in testes. Stimulates progesterone synthesis in women Stimulates ovulation and corpus luteum development.
33
FSH physiologic function?
Stimulates spermatogenesis in testes. | Stimulates estrogen synthesis by granulosa cells in ovarian follicles.
34
Prolactin physiologic actions?
Stimulates breast maturation and milk letdown.
35
What are the posterior pituitary hormones?
ADH | oxytocin
36
ADH physiologic function?
Stimulates water absorption from the distal nephron.
37
Oxytocin
Stimulates uterine contraction during labor.
38
What are the two thyroid hormones?
Thyroxine (T4) | Triiodothyronine (T3)
39
What is T4's physiologic function?
Prohormone that becomes bioactive on peripheral conversion to T3.
40
T3 physiologic action?
Increases basal metabolic rate by up-regulating expression and insertion of Na+, K+-ATPase pump
41
What are the adrenal cortex hormones?
Aldosterone Cortisol DHEA (dehydroepiandrosterone)
42
What are the physiologic functions of cortisol?
MAINTAIN GLUCOSE for glucose-dependent tissues during fasting state by promoting hepatic gluconeogenesis, peripheral resistance to insulin, lipolysis in adipose tissue.
43
DHEA function?
Converted to testosterone in peripheral tissues.
44
What are the adrenal medulla hormones?
Epinephrine
45
What are the ovarian hormones?
Estrogen
46
Testicular hormones?
Testosterone | DHT
47
Pancreatic hormones?
Insulin Glucagon Somatostatin Vasoactive-intestinal peptide
48
What two hormone binding proteins' plasma levels increase during pregnancy?
Thyroid binding globulin Transcortin Estrogen increases their synthesis in the liver. This will increase total thyroid and cortisol hormone but NOT free thyroid and cortisol hormone.
49
In primary endocrine diseases, where is the defect?
Defect is in the endocrine organ.
50
In secondary endocrine diseases, where is the defect?
Defect is in the pituitary gland.
51
In tertiary endocrine diseases, where is the defect?
The defect is in the hypothalamus.
52
What is the overall function of the hypothalamic-pituitary-adrenal axis?
Function is to maintain physiologically appropriate plasma levels of the hormone cortisol.
53
ACTH acts on adrenal cortex to stimulate the synthesis and secretion of glucocorticoids and androgens. Can androgens feedback-inhibit ACTH secretion?
NO, androgens to not feedback-inhibit the pituitary.
54
What physiological processes is cortisol secretion stimulated by?
``` Hypoglycemia Stressful conditions (surgery), when the sympathetic nervous system is also stimulated ```
55
What is cortisol sometimes referred to as?
Stress hormone
56
A tumor of the adrenal gland that autonomously hypersecretes cortisol will have what sort of effect on CRH, ACTH and cortisol?
It still will negatively feedback on the hypothalamus and anterior pituitary, resulting in decreased ACTH secretion. Patient will be hypercortisolemic with a low ACTH, implying an etiology is adrenal in origin.
57
When are cortisol levels highest?
Early morning, owing to the early-morning surge of ACTH.
58
What is the rate limiting step in adrenal steroid synthesis?
Conversion of cholesterol to pregnenolone.
59
Which adrenal steroid is synthesized in the zona glomerulosa? zona fasciculata? zona reticularis?
Remember "GFR" The deeper you go the sweeter it gets. G= Mineralcorticoids F= Cortisol R= androgens
60
The secretion of aldosterone is regulated by what?
Plasma concentrations of Potassium and angiotensin II, with the latter increasing conversion of corticosterone to aldosterone by stimulation of 18-hydroxylase.
61
How does cortisol stimulate hepatic gluconeogenesis?
Promotes muscle breakdown, release a.a. Ala and Asp into gluconeogenic pathway Stimulates synthesis of hepatic gluconeogenic enzymes Stimulates lipolysis in adipose tissue -> helps maintain plasma levels of glycerol and fatty acids in fasting state
62
Metabolic actions of cortisol?
Affects liver, muscle, adipose tissue. Generally catabolic Stimulates gluconeogenesis Preserves plasma glucose.
63
Does cortisol increase or decrease BP?
Increase.
64
At higher concentrations, cortisol can exert what sort of effects on the kidney?
Mineralocorticoid effect because it is similar in structure to aldosterone.
65
Does cortisol have inflammatory or anti-inflammatory effects?
Anti-inflammatory. | Inhibits activity of phospholipase A -> decreased arachidonic acid -> decreased prostaglandins and leukotrienes.
66
Does cortisol weaken or strengthen bone at supraphysiologic levels?
Cortisol WEAKENS bone by inhibiting osteoblasts and stimulating osteoclasts.
67
Name four things that cortisol promotes and the pathophysiologic conditions associated with each.
Hyperglycemia -> Diabetes mellitus Muscle breakdown -> muscle wasting Bone Loss -> osteoporosis Plasma volume expansion -> hypertension
68
What is the most common endogenous source of elevated cortisol?
ACTH-hypersecreting tumor of the pituitary, also known as Cushing DISEASE
69
What does the dexamethasone test determine? How is it done?
Test differentiates between pituitary Cushing and paraneoplastic secretion ACTH in patient with hypercortisolism and elevated ACTH. Pituitary Cushing - has feedback inhibition Ectopic Cushing - not controlled thru feedback inhibition
70
What is the most common cause of hypocortisolism?
Iatrogenic. Abrupt cessation of chronically administered steroids.
71
In primary adrenal insufficiency, are ACTH levels high or low?
High.
72
What is a major cause of chronic adrenal insufficiency?
Autoimmune destruction of the adrenals (Addison's Disease), tuberculosis or metastatic cancer involving the adrenals can also be a cause of chronic adrenal insufficiency.
73
Signs and symptoms of adrenal insufficiency?
Hypotension Salt Wasting High levels of ACTH hyperpigmentation of the skin
74
Congenital Adrenal Hyperplasias (CAH) are characterized by enzymatic defects in what pathway?
Cortisol biosynthetic pathway.
75
What is the most common form of CAH?
21-hydroxylase deficiency
76
Why does 11-hydroxylase deficiency produce salt retention and hypertension?
Because of an increase in 11-deoxycorticosterone, which is proximal to the enzyme block.
77
What is the main function of the hypothalamic-pituitary-thyroid axis?
Maintain physiologically appropriate plasma levels of thyroid hormones T3 and T4
78
TSH stimulates secretion of T3 and T4 from what cells in the thyroid gland?
Follicular cells
79
What hormone, secreted by the parafollicular cells in the thyroid gland, is NOT regulated by the hypothalamus-pituitary-thyroid axis?
Calcitonin
80
Describe the steps in the synthesis of thyroid hormone
(I-) internalized (TSH mediated) (I-) to I2 I2 attached to thyroglobulin -> MIT DIT (TSH mediated) Couple MIT + DIT into T4 and T3 Endocytosis of thyroglobulin from colloid Hydrolytic cleavage of T3 and T4 from thyroglobulin; diffusion of T4 and T3 into plasma (TSH mediated)
81
Common drugs to treat hyperthyroidism?
Propylthiouracil (PTU) | Methimazole
82
T4 is more or less potent than T3?
T4 is much LESS potent than T3 but has a longer plasma half-life than T3.
83
What enzyme converts T4 to T3?
5'-monodeiodinase.
84
Is T4 or T3 responsible for feedback inhibition of pituitary and hypothalamus?
T4; much more abundant
85
What systems do thyroid hormones act on?
Metabolism, Bone, CNS, Skin, CV system, Intestines.
86
What is the most common cause of hyperthyroidism?
Graves Disease (diffuse toxic goiter)
87
Most common type of secondary hyperthyroidism?
Pituitary Adenoma
88
Most common cause of tertiary hyperthyroidism?
Hypothalamic tumor.
89
What is the classical presentation of Grave's Disease?
thyrotoxicosis (symptoms of hyperthyroidism) diffuse goiter ophthalmopathy (exophthalmos) dermopathy (pretibial myxedema)

ENDOREPRO MODULE (11 decks)

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