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The reproductive system and toxic effects Flashcards

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1
Q

What are the three components of the endocrine system?

A
  1. Endocrine gland that secretes hormones
  2. Hormone itself
  3. Target tissue

The endocrine system regulates the internal environment of higher animals independent of external factors.

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2
Q

How do hydrophilic hormones differ from hydrophobic hormones?

A

Hydrophilic hormones (peptides and proteins) are freely dissolved in plasma, while hydrophobic hormones (steroids, amino acid derivatives) bind to specialized serum binding proteins or albumin.

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3
Q

Where are hormone receptors located for different types of hormones?

A

Receptors can be located on the plasma membrane (for peptides, proteins, and catecholamines) or in the cellular nucleus (for steroids, thyroid, and vitamin D hormones).

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4
Q

What are the four major subdivisions of the pituitary gland?

A
  1. Pars distalis (adenohypophysis or anterior pituitary)
  2. Pars intermedia
  3. Pars tuberalis
  4. Pars nervosa (neurohypophysis or posterior pituitary).
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5
Q

How does the anterior pituitary receive signals from the hypothalamus?

A

The anterior pituitary receives endocrine input from the hypothalamus in the form of peptide releasing hormones transported in portal vessels.

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6
Q

What is the function of vasopressin (ADH) secreted by the posterior pituitary?

A

ADH enhances reabsorption of water in the kidneys and causes contraction of vascular smooth muscle.

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7
Q

What role does oxytocin play in the body?

A

Oxytocin stimulates contraction of smooth muscles in the uterine myometrium and breast alveoli.

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8
Q

True or False: Cadmium exposure has no effect on pituitary hormone secretion.

A

False.

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9
Q

Which hormones does the adrenal cortex secrete?

A
  1. Aldosterone (mineralocorticoid)
  2. Cortisol and corticosterone (glucocorticoids)
  3. Dehydroepiandrosterone and androstenedione (androgens).
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10
Q

What physiological functions does the adrenal cortex regulate?

A
  1. Immune system
  2. Inflammation
  3. Water and electrolyte balance
  4. Carbohydrate and protein metabolism.
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11
Q

What is the primary precursor for the synthesis of adrenal steroids?

A

Cholesterol.

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12
Q

Fill in the blank: The adrenal cortex is predisposed to the toxic effects of _______ chemicals.

A

xenobiotic.

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13
Q

What is the effect of glucocorticoids on glucose production?

A

They increase hepatic glucose production through gluconeogenesis.

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14
Q

What are some compounds known to produce necrosis in the adrenal cortex?

A
  1. 7,12-dimethylbenz[a]anthracene (DMBA)
  2. Acrylonitrile
  3. Thioacetamide.
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15
Q

What is the role of corticosteroid binding globulin (CBG)?

A

CBG transports cortisol and corticosterone in blood and keeps the steroid biologically inactive.

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16
Q

How do xenobiotic compounds affect adrenocortical receptors?

A

They can upregulate or downregulate the receptors located in target tissues.

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17
Q

What initiates the secretion of cortisol from the adrenal cortex?

A

The pituitary hormone ACTH stimulates the zonae fasciculata and reticularis.

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18
Q

What happens to the adrenal cortex during chronic stress?

A

Persistent exposure to high levels of ACTH can result in adrenocortical hypertrophy.

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19
Q

What is the role of cortisol in the hypothalamic-pituitary-adrenal axis?

A

Cortisol provides long-loop negative feedback on the hypothalamus and anterior pituitary, decreasing CRH and ACTH secretion.

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20
Q

What factor can override the negative feedback control system of cortisol secretion?

A

Stress

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21
Q

What is a consequence of persistent exposure of the adrenal cortex to high levels of ACTH during chronic stress?

A

Adrenocortical hypertrophy

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22
Q

What occurs when there is reduced exposure of the adrenal cortex to ACTH?

A

Adrenal atrophy

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23
Q

Which hormones are primarily involved in the regulation of aldosterone secretion?

A

Renin and angiotensin II

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24
Q

What is the function of aldosterone?

A

Promotes sodium reabsorption and increases excretion of potassium and hydrogen ions by the kidney.

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25
What initiates the release of renin from the juxtaglomerular apparatus?
Decreases in blood pressure or volume, or reduced plasma sodium
26
What is the specialized fetal adrenal cortex responsible for during late gestation?
Producing abundant cortisol and estrogen precursors
27
What happens to the fetal adrenal cortex after birth?
Rapid regression, apoptosis, and lysis, replaced by the typical three cortical zones.
28
What is the X-zone in the mouse adrenal cortex?
A unique physiological phenomenon that develops postnatally in the inner cortex of mice.
29
What is the primary function of the adrenal medulla?
Synthesis and secretion of catecholamines.
30
What are the main types of adrenergic receptors?
* α adrenoceptors * β adrenoceptors
31
What is pheochromocytoma?
A benign adrenal medullary proliferative lesion composed of chromaffin cells.
32
What effect do exogenous steroids have on ACTH secretion?
Cause negative feedback inhibition of ACTH secretion.
33
Fill in the blank: The adrenal medulla is a functional extension of the _______.
nervous system
34
What type of stimulation causes catecholamine release from chromaffin cells?
Sympathetic, cholinergic stimulation
35
What are the physiological activators of catecholamine release?
* Decreased blood pressure * Decreased blood glucose * Decreased oxygen availability * Stress or anxiety * Cold * Exercise * Postural hypotension
36
What is the primary structure of thyroid hormones?
Two modified, covalently linked tyrosine amino acids with iodides.
37
What is the primary function of thyroid hormones T3 and T4?
Regulators of overall metabolism
38
What is thyroglobulin (TGB)?
A glycoprotein that serves as the backbone for thyroid hormone synthesis.
39
What is the primary effect of xenobiotics on thyroid hormone synthesis?
Interfere with the process of thyroid hormone synthesis.
40
What happens to the majority of thyroid hormones in circulation?
They are bound to high-affinity serum binding proteins.
41
What are the three types of thyroid hormone binding proteins?
* Thyroid binding globulin * Thyroxine-binding prealbumin (TBPA) * Albumin
42
What are thyroid hormone receptors (TRs)?
Members of the nuclear receptor superfamily of ligand-inducible transcription factors.
43
True or False: Environmental chemicals can interfere with thyroid hormone binding to receptors.
True
44
What are the three thyroid hormone receptor isoforms?
TRα, TRβ1, TRβ2 ## Footnote These isoforms play a critical role in the regulation of thyroid hormone action in the body.
45
What is one way environmental chemicals interfere with thyroid hormone binding?
They bind directly to TRs and induce agonistic or antagonist effects ## Footnote This can disrupt normal thyroid hormone activity.
46
How can environmental chemicals affect thyroid hormone binding indirectly?
By promoting coactivators or inhibiting corepressors ## Footnote This disruption can alter the transcriptional activity of thyroid hormones.
47
What is the main pathway for clearance of thyroid hormones from the serum?
Conjugation to glucuronic acid or sulfate ## Footnote This process allows for the elimination of thyroid hormones.
48
Which proteins transport thyroid hormone metabolites across plasma membranes?
Multidrug resistance protein 1 and multidrug resistance–associated protein 2 (MRP2) ## Footnote These proteins play a crucial role in hormone clearance.
49
What hormone regulates thyroid hormone secretion?
Thyroid-stimulating hormone (TSH, thyrotropin) ## Footnote TSH is secreted from the anterior pituitary gland.
50
How does the hypothalamic–pituitary–thyroid axis function?
Hypothalamic TRH stimulates TSH release, which then increases T4 and T3 secretion ## Footnote This axis involves negative feedback mechanisms.
51
What is the primary feedback mechanism of thyroid hormones on TSH?
T4 and T3 inhibit TSH release primarily at the anterior pituitary ## Footnote This feedback helps regulate thyroid hormone levels.
52
What is the circadian rhythm of TRH and TSH release?
There is a decrease following the onset of sleep ## Footnote This rhythm is not reflected in circulating thyroid hormone concentrations.
53
What are the physiological effects of thyroid hormones?
Determine overall metabolic rate, stimulate anabolic and catabolic pathways ## Footnote Their primary effect is catabolism and energy mobilization.
54
What can xenobiotics that affect thyroid hormone levels cause?
Symptoms of hypothyroidism, hyperthyroidism, and impairment in brain development ## Footnote These effects can lead to significant health issues.
55
How do PCBs affect thyroid hormone levels?
They inhibit synthesis and/or increase metabolism by inducing phase II enzymes ## Footnote This can lead to neurocognitive effects, especially in prenatal exposure.
56
What is one way PBDEs disrupt thyroid function?
By inducing hepatic phase II enzymes and downregulating transport proteins ## Footnote This disruption can lead to serious neurocognitive deficits.
57
What effect does perchlorate have on thyroid hormone synthesis?
It inhibits synthesis primarily by reducing iodide uptake ## Footnote This can lead to decreased thyroid hormone levels.
58
What are the effects of organochlorine pesticides on thyroid hormones?
Increase TSH and decrease T4 in a male agricultural population ## Footnote They can also induce autoimmune thyroid disease.
59
What is the effect of perfluorinated chemicals like PFOS and PFOA on thyroid hormones?
They alter T3 and T4 levels by affecting phase II metabolic enzymes ## Footnote This can disrupt normal thyroid hormone regulation.
60
What does Bisphenol A (BPA) block?
T3 binding to its receptor ## Footnote BPA exposure can lead to various thyroid dysfunctions.
61
Fill in the blank: Phthalates may alter levels of T4 and T3 by inhibiting _______.
thyroperoxidase ## Footnote This inhibition can lead to low thyroid hormone levels and symptoms of hypothyroidism.
62
What are the locations of the parathyroid glands in humans?
On the back side of the thyroid gland.
63
What is the primary function of parathyroid hormone (PTH)?
Helps maintain normal plasma calcium levels.
64
What happens when parathyroid glands are removed or damaged?
PTH levels drop, causing a major drop in circulating calcium levels.
65
What physiological effects can result from low circulating calcium levels?
Tetanic convulsions and death.
66
Which cells primarily comprise the parathyroid glands?
Chief cells.
67
Name a chemical that causes degenerative changes in the parathyroid gland.
l-asparaginase.
68
What is the precursor molecule from which PTH is derived?
Preproparathyroid hormone.
69
Which xenobiotics have been shown to inhibit PTH secretion?
Aluminum and cadmium.
70
What is the PTH receptor known as?
PTHR1.
71
Where is PTHR1 extensively localized?
In bone and kidney cells.
72
What is the primary site of PTH metabolism?
Liver and kidney.
73
What role does PTH play in calcium levels?
Increases circulating calcium levels.
74
What does calcitonin (CT) do in relation to calcium levels?
Reduces circulating calcium levels.
75
Which vitamin inhibits PTH actions and is essential for calcium absorption?
Vitamin D3 (cholecalciferol).
76
What happens to PTH secretion with xenobiotic exposure to heavy metals?
It may cause low PTH secretion and lead to hypoparathyroidism.
77
What stimulates the release of PTH?
Low calcium levels sensed by calcium receptors.
78
What is the primary function of the endocrine pancreas?
Regulate fuel metabolism, particularly circulating glucose.
79
What is the most abundant cell type in the Islets of Langerhans?
Beta cells (β).
80
What is the primary effect of insulin?
Stimulate anabolic processes and lower blood glucose levels.
81
What stimulates the release of glucagon?
Epinephrine, norepinephrine, and specific amino acids.
82
What is the counter-regulatory hormone to insulin?
Glucagon.
83
True or False: Somatostatin inhibits the secretion of insulin.
True.
84
What is the consequence of inadequate insulin action?
Diabetes mellitus.
85
What characterizes Type 1 diabetes?
Autoimmune-based destruction of pancreatic β cells.
86
What is a common method to induce diabetes in animal models?
Using alloxan and streptozotocin (STZ).
87
What condition is often associated with exposure to dioxins and mercury?
Insulin resistance.
88
What happens to pancreatic β cells when exposed to oxidative stress?
Elevated proapoptotic markers and potential cell toxicity.
89
Fill in the blank: The liver is the primary contributor to increasing blood glucose levels through _______.
glycogen breakdown (glycogenolysis) and de novo synthesis (gluconeogenesis).

Medical Toxicology (13 decks)

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