Chapters 21/22 Flashcards
(147 cards)
1
Q
What are the diverse functions of the endocrine system?
A
The endocrine system includes reproductive and CNS differentiation, growth and development, coordination of reproductive systems, maintenance of the body’s internal environment, and stress responses.
2
Q
What are hormones?
A
Hormones are chemical messengers synthesized by endocrine glands and released into circulation, working with the nervous and immune systems to maintain communication and control.
3
Q
What are the feedback mechanisms for hormones?
A
Hormones have negative- and positive-feedback mechanisms. Most are regulated by negative feedback, where elevated hormone levels decrease tropic hormone secretion. Positive feedback is common in reproductive hormones.
4
Q
What are the types of endocrine feedback?
A
Endocrine feedback can be described in terms of long and short feedback loops.
5
Q
How do hormones communicate within the body?
A
Endocrine communications occur within cells (autocrine), between cells (paracrine), and between remote cells (endocrine).
6
Q
How do water-soluble and lipid-soluble hormones circulate?
A
Water-soluble hormones circulate unbound, while lipid-soluble hormones circulate bound to carrier proteins.
7
Q
What are target cells?
A
Hormones affect only cells with appropriate receptors (target cells) to initiate specific functions or activities.
8
Q
What are the two general types of effects hormones have on cells?
A
Hormones have direct effects (obvious changes in cell function) and permissive effects (less obvious changes that facilitate cell function).
9
Q
Where are hormone receptors located?
A
Receptors for hormones are large proteins located on or in the plasma membrane, cytosol, or nucleus of the target cell.
10
Q
What are first messengers and second messengers?
A
Water-soluble hormones act as first messengers, binding to receptors on the plasma membrane. Second messengers transmit signals into the cell.
11
Q
What are some identified second messengers?
A
Identified second messengers include cAMP, cGMP, and calcium.
12
Q
How does cAMP function as a second messenger?
A
For cells with cAMP, interactions within the plasma membrane activate adenylyl cyclase.
13
Q
How does cGMP function as a second messenger?
A
Cells with cGMP are activated by the enzyme guanylyl cyclase.
14
Q
What happens when calcium acts as a second messenger?
A
Increased intracellular calcium binds with calmodulin, initiating other intracellular processes.
15
Q
How do lipid-soluble hormones exert effects?
A
Lipid-soluble hormones may have rapid effects by binding to receptors or crossing the plasma membrane to bind to cytoplasmic or nuclear receptors.
16
Q
What is the hypothalamic-pituitary axis (HPA)?
A
The HPA forms the structural and functional basis for central integration of the neurologic and endocrine systems.
17
Q
How does the hypothalamus regulate the anterior pituitary?
A
The hypothalamus regulates anterior pituitary function by secreting releasing hormones into the portal circulation.
18
Q
What hormones are secreted by the hypothalamus?
A
Hypothalamic hormones include dopamine, TRH, CRH, and substance P, with ADH and oxytocin synthesized in the hypothalamus.
19
Q
What does ADH do?
A
ADH controls serum osmolality, increases renal tubule permeability to water, and causes vasoconstriction at high doses.
20
Q
What is the role of oxytocin?
A
Oxytocin causes uterine contraction and lactation in women and may aid sperm motility in men.
21
Q
How are anterior pituitary hormones regulated?
A
Anterior pituitary hormones are regulated by hypothalamic-releasing hormones, negative feedback from target organs, and neurotransmitters.
22
Q
What hormones are produced by the anterior pituitary?
A
Hormones include ACTH, MSH, GH, prolactin, FSH, LH, and TSH.
23
Q
What is the function of growth hormone?
A
Growth hormone stimulates bone growth, protein metabolism, and lipolysis, mediated by IGFs.
24
Q
What is the function of prolactin?
A
Prolactin is responsible for milk production during pregnancy and lactation.
25
What does the pineal gland produce?
The pineal gland produces melatonin, affecting sleep, circadian rhythms, and immune function.
26
What is the structure of the thyroid gland?
The thyroid gland contains follicles that secrete thyroid hormones and parafollicular cells that secrete calcitonin.
27
How is thyroid hormone (TH) secretion regulated?
TH secretion is regulated by TRH through a negative-feedback loop involving the anterior pituitary and hypothalamus.
28
What is the role of TSH?
TSH stimulates TH secretion by activating intracellular processes, including iodine uptake.
29
What is required for TH synthesis?
TH synthesis depends on thyroglobulin, which contains tyrosine that combines with iodide to form T4 and T3.
30
How are T3 and T4 transported in the body?
T3 and T4 are bound by carrier proteins in the plasma, providing a buffer for hormone levels.
31
What effects do thyroid hormones have?
Thyroid hormones alter protein synthesis and have metabolic effects on proteins, carbohydrates, lipids, and vitamins.
32
What do parathyroid glands secrete?
Parathyroid glands secrete PTH, the main regulator of serum calcium and phosphate levels.
33
How is PTH secretion regulated?
PTH secretion is regulated by ionized calcium levels in plasma and cAMP within the cell.
34
What are the effects of PTH in the body?
PTH causes bone resorption, increases calcium reabsorption in the kidneys, and stimulates vitamin D synthesis.
35
What is PTHrP?
PTHrP has properties similar to PTH and plays roles in placental calcium transport and fetal development.
36
What is the function of the islets of Langerhans?
The islets of Langerhans secrete hormones that regulate carbohydrate metabolism.
37
What do alpha cells produce?
Alpha cells produce glucagon, which stimulates glycogenolysis, gluconeogenesis, and lipolysis.
38
What is the role of beta cells?
Beta cells synthesize insulin, regulating blood glucose and overall metabolism.
39
What additional hormone do beta cells secrete?
Beta cells also secrete amylin, which promotes insulin secretion and inhibits glucagon synthesis.
40
What do delta cells secrete?
Delta cells secrete pancreatic somatostatin, inhibiting glucagon and insulin secretion.
41
What do F cells secrete?
F cells secrete pancreatic polypeptide, stimulating gastric secretion and antagonizing cholecystokinin.
42
What are incretin hormones?
Incretin hormones promote glucose-dependent insulin secretion and inhibit glucagon synthesis.
43
What is the structure of the adrenal glands?
The adrenal glands consist of an adrenal medulla that secretes catecholamines and an adrenal cortex that secretes steroid hormones.
44
What hormones are secreted by the adrenal cortex?
The adrenal cortex secretes glucocorticoids, mineralocorticoids, and adrenal androgens and estrogens.
45
What is the effect of glucocorticoids?
Glucocorticoids increase blood glucose through gluconeogenesis and inhibit immune responses.
46
How is cortisol secretion regulated?
Cortisol secretion is related to ACTH secretion, which is stimulated by CRH.
47
What do mineralocorticoids do?
Mineralocorticoids affect ion transport, causing sodium retention and potassium loss.
48
How is aldosterone secretion controlled?
Aldosterone secretion is controlled by the renin-angiotensin-aldosterone system.
49
What is the role of adrenal androgens and estrogens?
Adrenal androgens and estrogens act similarly to those secreted by the gonads.
50
What does the adrenal medulla secrete?
The adrenal medulla secretes catecholamines, including epinephrine and norepinephrine.
51
What stimulates catecholamine release?
Catecholamine release is stimulated by sympathetic nervous system activation, ACTH, and glucocorticoids.
52
What is the fight or flight response?
Catecholamines cause metabolic effects characterized as the 'fight or flight' response.
53
How does the endocrine system respond to stress?
The endocrine system works with the nervous and immune systems to provide an integrated response to stressors.
54
What assay methods measure hormone levels?
Assay methods include RIA, ELISA, and bioassays.
55
What is RIA?
RIA compares radiolabeled and nonradiolabeled hormone proportions against standard curves.
56
What is ELISA?
ELISA is similar to RIA but uses a radiolabeled enzyme instead of a radiolabeled hormone.
57
What do bioassays do?
Bioassays use graded hormone doses in a reference preparation to compare results with an unknown sample.
58
What endocrine changes are associated with aging?
Aging may alter hormone activity, circulating levels, secretory responses, metabolism, circadian control, and hypothalamic hormone secretion.
59
What contributes to endocrine gland dysfunction with aging?
Cellular damage, genetically programmed changes, and chronic wear and tear may contribute to dysfunction.
60
How does aging affect the thyroid gland?
Aging causes thyroid gland atrophy and may diminish thyroid hormone secretion.
61
What happens to insulin secretion with aging?
Aging leads to pancreatic fat deposition, decreased insulin secretion, and reduced insulin sensitivity.
62
How does aging affect growth hormone levels?
Growth hormone levels decrease with aging, leading to reduced bone and muscle mass.
63
What changes occur in calcium steady states with aging?
Aging is associated with alterations in calcium steady states, possibly related to PTH secretion changes.
64
What age-related changes occur in adrenal function?
Aging leads to decreased glucocorticoid clearance and lower adrenal androgen levels.
65
What is the Klotho protein?
Klotho protein, secreted by the kidney, choroid plexus, and parathyroid gland, has antiaging effects.
66
What causes abnormalities in endocrine function?
Abnormalities may be caused by hypersecretion or hyposecretion of hormones or alterations in transport molecules.
67
What mechanisms can alter receptor function in endocrine abnormalities?
Alterations can occur through a decrease in the number of receptors, receptor insensitivity, presence of antibodies against specific receptors, and defects in second-messenger generation or postreceptor defects.
68
What are ectopic foci in relation to hormone secretion?
Ectopic foci are tissues outside the endocrine system that release hormones autonomously, not responding to normal feedback mechanisms.
69
What is the relationship between hypothalamic hormone release and the pituitary stalk?
Dysfunction in the release of hypothalamic hormones is likely related to interruption of the connection between the hypothalamus and pituitary—namely, the pituitary stalk.
70
What disorders are associated with the posterior pituitary?
Disorders include SIADH secretion, characterized by high ADH secretion, and DI, characterized by low ADH secretion.
71
What are the effects of high ADH levels in SIADH?
High ADH levels interfere with renal free water clearance, leading to hyponatremia and hypoosmolality. SIADH is associated with certain cancers due to ectopic ADH secretion.
72
What causes DI and what are its clinical features?
DI may be neurogenic (insufficient ADH) or nephrogenic (inadequate response to ADH), leading to failure to concentrate urine, polyuria, and polydipsia.
73
What is hypopituitarism?
Hypopituitarism is dysfunction of the anterior pituitary causing failure of hormonal functions, with symptoms varying from mild to severe.
74
What are the causes of hypopituitarism?
Causes include pituitary infarction, space-occupying lesions, surgical removal, or infections, with symptoms depending on deficient hormones.
75
What is hyperpituitarism and what causes it?
Hyperpituitarism is caused by pituitary adenomas, which are usually benign tumors arising from anterior pituitary cells.
76
What are the effects of a pituitary adenoma?
Expansion causes neurologic and secretory effects, including hyposecretion of cells, visual disturbances, and dysfunction of the hypothalamus.
77
What does hypersecretion of GH cause?
Hypersecretion of GH causes acromegaly in adults and giantism in children, with pituitary adenoma being the most common cause.
78
What are the consequences of prolonged high levels of GH?
Prolonged high GH levels lead to tissue proliferation, renal, thyroid, cardiovascular, and reproductive dysfunctions, along with insulin resistance.
79
What are the effects of GH deficiency in children and adults?
GH deficiency in children results in growth failure and hypoglycemia; in adults, it causes fatigue, osteoporosis, and increased mortality.
80
What can increase prolactin levels?
Pituitary prolactinomas, renal failure, and medications can increase prolactin levels, affecting reproductive organs in both genders.
81
What is thyrotoxicosis?
Thyrotoxicosis is a condition with elevated TH levels producing exaggerated physiological responses, which can be primary, secondary, or subclinical.
82
What are the manifestations of hyperthyroidism?
Hyperthyroidism manifests through endocrine, reproductive, gastrointestinal, integumentary, and ocular symptoms due to increased TH levels.
83
What causes Graves disease?
Graves disease is caused by thyroid-stimulating immunoglobulins stimulating TSH receptors, leading to thyroid hyperplasia and increased TH synthesis.
84
What are the symptoms of Graves disease?
Symptoms include hyperthyroidism, diffuse thyroid enlargement, and skin and eye disorders.
85
What is pretibial myxedema?
Pretibial myxedema is a cutaneous manifestation of Graves disease characterized by subcutaneous swelling of the legs and sometimes hands.
86
What ocular manifestations are associated with Graves disease?
Ocular manifestations result from sympathetic hyperactivity and immune-induced infiltration, leading to exophthalmos.
87
What causes toxic multinodular goiter?
Toxic multinodular goiter occurs when hyperplastic thyroid nodules autonomously secrete TH, causing hyperthyroidism.
88
What is a thyrotoxic crisis?
Thyrotoxic crisis (thyroid storm) is a severe form of hyperthyroidism associated with physiological stress, leading to rapid deterioration.
89
What causes hypothyroidism?
Hypothyroidism is caused by deficient TH production by the thyroid gland and can be primary, secondary, or subclinical.
90
What are the causes of primary hypothyroidism?
Causes include iodine deficiency, autoimmune thyroiditis, and various forms of thyroiditis.
91
What is autoimmune thyroiditis (Hashimoto disease)?
Hashimoto disease involves lymphocyte infiltration and antibody activation leading to gradual loss of thyroid function and hypothyroidism.
92
What is subacute thyroiditis?
Subacute thyroiditis is a self-limited inflammation of the thyroid that can lead to transient hyperthyroidism followed by hypothyroidism.
93
What is secondary hypothyroidism?
Secondary hypothyroidism is due to hypothalamic-pituitary dysfunction, resulting in insufficient TRH and TSH production.
94
What is the most consistent risk factor for thyroid carcinoma?
Exposure to ionizing radiation, especially during childhood, is the most consistent risk factor for thyroid carcinoma.
95
What are common symptoms of hypothyroidism?
Symptoms include decreased energy metabolism and loss of heat production.
96
What is myxedema?
Myxedema is a characteristic sign of hypothyroidism caused by alterations in connective tissue, leading to edema.
97
What is myxedema coma?
Myxedema coma is a severe, potentially life-threatening form of hypothyroidism requiring emergency treatment.
98
What is congenital hypothyroidism?
Congenital hypothyroidism is TH deficiency at birth, leading to growth failure and intellectual disability.
99
What are the most common thyroid malignancies?
Papillary and follicular thyroid carcinomas are the most common, likely caused by ionizing radiation exposure.
100
What characterizes hyperparathyroidism?
Hyperparathyroidism is characterized by greater than normal secretion of PTH and can be primary, secondary, or tertiary.
101
What causes primary hyperparathyroidism?
Primary hyperparathyroidism is usually caused by a parathyroid adenoma, leading to chronic hypercalcemia and increased bone resorption.
102
What is secondary hyperparathyroidism?
Secondary hyperparathyroidism is a compensatory response to hypocalcemia, often due to chronic renal failure or vitamin D deficiency.
103
What is tertiary hyperparathyroidism?
Tertiary hyperparathyroidism is excessive PTH secretion and hypercalcemia that occurs after long-standing hypocalcemia.
104
What is pseudohypoparathyroidism?
Pseudohypoparathyroidism is an inherited condition characterized by resistance to PTH.
105
What causes hypoparathyroidism?
Hypoparathyroidism is caused by thyroid surgery, autoimmunity, or genetic mechanisms, leading to low PTH levels.
106
What are the consequences of low PTH in hypoparathyroidism?
Low PTH causes depressed serum calcium levels, increased serum phosphate levels, decreased bone resorption, and hypocalciuria.
107
What is diabetes mellitus?
Diabetes mellitus is a group of diseases characterized by hyperglycemia due to defects in insulin secretion or action.
108
How is diabetes mellitus diagnosed?
Diagnosis is based on HbA1c levels, fasting plasma glucose levels, and 2-hour plasma glucose levels during OGTT.
109
What is type 1 diabetes mellitus?
Type 1 diabetes includes an autoimmune type (type 1A) associated with destruction of pancreatic beta cells and a nonimmune type (type 1B) secondary to other diseases.
110
What causes type 2 diabetes mellitus?
Type 2 diabetes is caused by genetic susceptibility triggered by environmental factors, primarily obesity.
111
What mechanisms contribute to insulin resistance in type 2 diabetes?
Mechanisms include altered adipokine production, elevated free fatty acids, inflammatory cytokines, and reduced mitochondrial activity.
112
What is the role of amylin in type 2 diabetes?
Amylin deficiency in type 2 diabetes leads to increased glucagon secretion and hyperglycemia.
113
What are other specific types of diabetes mellitus?
Other types include MODY associated with gene mutations and gestational diabetes related to glucose intolerance during pregnancy.
114
What are acute complications of diabetes mellitus?
Acute complications include hypoglycemia, DKA, HHNKS, the Somogyi effect, and the dawn phenomenon.
115
What is hypoglycemia?
Hypoglycemia is a lowered blood glucose level that can be related to exogenous, endogenous, or functional causes.
116
What are the symptoms of hypoglycemia?
Symptoms are divided into adrenergic (activation of the sympathetic nervous system) and neuroglycopenic (defective CNS metabolism).
117
What causes DKA?
DKA develops from insulin deficiency and increased insulin counter-regulatory hormones, leading to lipolysis and ketogenesis.
118
What is HHNKS?
HHNKS is similar to DKA but with lower FFA levels and no ketosis, leading to osmotic diuresis and dehydration.
119
What is the Somogyi effect?
The Somogyi effect is hypoglycemia followed by rebound hyperglycemia due to counter-regulatory hormones, common in type 1 diabetes.
120
What is the dawn phenomenon?
The dawn phenomenon is an early morning rise in glucose levels caused by nocturnal GH elevation.
121
What are chronic complications of diabetes mellitus?
Chronic complications include microvascular disease, macrovascular disease, and infections related to chronic hyperglycemia.
122
What causes diabetic retinopathy?
Diabetic retinopathy is caused by microvascular changes and thrombosis leading to vision loss.
123
What is diabetic nephropathy?
Diabetic nephropathy is related to hyperglycemia and inflammation, leading to renal failure.
124
What causes diabetic neuropathies?
Diabetic neuropathies may result from vascular and metabolic mechanisms, affecting nerve conduction and the autonomic nervous system.
125
What is macrovascular disease in diabetes?
Macrovascular disease is associated with hyperglycemia and inflammation, leading to increased risk of CAD and stroke.
126
What is the risk of coronary heart disease in diabetes?
Individuals with diabetes have a greater incidence of coronary heart disease, peripheral vascular disease, and stroke.
127
What causes peripheral artery disease in diabetes?
Peripheral artery disease results from neuropathy and artery occlusion, increasing the risk of ischemia and necrosis.
128
What infections are individuals with diabetes at risk for?
Individuals are at risk for infections due to sensory impairment, vascular complications, and impaired immunity.
129
What disorders are associated with adrenal cortex dysfunction?
Disorders are related to hyperfunction or hypofunction, with no known disorders linked to adrenal medulla hypofunction.
130
What is hypercortisolism?
Hypercortisolism is divided into ACTH-dependent (Cushing disease) and ACTH-independent (adrenal adenoma) mechanisms.
131
What is Cushing disease?
Cushing disease is excessive ACTH production from an ACTH-secreting pituitary microadenoma.
132
What is Cushing syndrome?
Cushing syndrome occurs with excessive cortisol levels, regardless of the cause, including exogenous glucocorticoids.
133
What are the effects of Cushing disease on ACTH and cortisol secretion?
Individuals lose diurnal patterns of ACTH and cortisol secretion and cannot increase secretion in response to stress.
134
What is congenital adrenal hyperplasia?
Congenital adrenal hyperplasia is an autosomal recessive disorder leading to inadequate cortisol synthesis and adrenal hyperplasia.
135
What characterizes primary hyperaldosteronism?
Primary hyperaldosteronism is excessive aldosterone secretion, usually from an adrenal adenoma, causing hypertension and hypokalemia.
136
What is secondary hyperaldosteronism?
Secondary hyperaldosteronism is related to conditions that elevate renin levels, leading to increased aldosterone secretion.
137
What is congenital adrenal hyperplasia?
An autosomal recessive disorder with inadequate synthesis of cortisol and increased levels of ACTH that cause adrenal hyperplasia and overproduction of mineralocorticoids or androgens.
138
What causes primary hyperaldosteronism?
Excessive aldosterone secretion usually caused by an adrenal cortical adenoma or bilateral nodular hyperplasia.
## Footnote
Characterized by hypertension, hypokalemia, renal potassium wasting, and neuromuscular manifestations.
139
What is secondary hyperaldosterone secretion related to?
A variety of conditions associated with elevated renin release and activation of angiotensin II, including decreased circulating blood volume, decreased renal blood supply, elevated estrogen levels, Bartter syndrome, and renin-secreting tumors.
140
What can adrenal tumors secrete?
Androgens or estrogens autonomously.
141
What can hypofunction of the adrenal cortex affect?
Glucocorticoid or mineralocorticoid secretion or both, caused by a deficiency of ACTH or a primary deficiency in the gland itself.
142
What is hypocortisolism?
Low levels of cortisol caused by inadequate adrenal stimulation by ACTH or by primary cortisol hyposecretion.
## Footnote
Primary adrenal insufficiency is termed Addison disease.
143
What characterizes Addison disease?
Elevated ACTH levels with inadequate corticosteroid synthesis and output.
## Footnote
Causes include idiopathic autoimmune disease, tuberculosis of the adrenal gland, familial adrenal insufficiency, amyloidosis, metastatic destruction of the adrenal glands, and adrenal hemorrhage.
144
What are the manifestations of Addison disease?
Related to hypocortisolism and hypoaldosteronism, including weakness, fatigability, hypoglycemia, lowered response to stressors, vitiligo, hyperpigmentation, and manifestations of hypovolemia and hyperkalemia.
145
What is secondary hypercortisolism characterized by?
Low to absent ACTH levels, leading to inadequate adrenal stimulation, adrenal atrophy, and decreased corticosteroidogenesis.
## Footnote
Most common cause is withdrawal of exogenous administration of glucocorticoids.
146
What causes hyperfunction of the adrenal medulla?
A pheochromocytoma, which is a catecholamine-producing tumor.
147
What are the symptoms of catecholamine excess?
Related to sympathetic nervous system effects, including hypertension, palpitations, tachycardia, glucose intolerance, excessive sweating, and constipation.
