Hormones Flashcards
1
Q
What does the endocrine system consist of?
A
Organs that secrete hormones into the blood, known as endocrine glands.
2
Q
What are the 3 types of hormone actions?
A
Autocrine, paracrine, or endocrine (acting on distant organs).
3
Q
What are the 3 main classes of hormones based on chemical nature?
A
Steroid hormones, peptide hormones, and amino acid-derived hormones.
4
Q
How do steroid hormones travel in the blood?
A
Either free or bound to a carrier protein.
5
Q
What kind of feedback loop is endocrine feedback primarily based on?
A
Negative feedback (with some examples of positive feedback, like oxytocin in parturition).
6
Q
Where is the pituitary gland located?
A
At the base of the brain, below the hypothalamus, near the optic chiasm.
7
Q
What is the role of the pituitary gland?
A
Master endocrine gland that controls other endocrine glands.
8
Q
What are the two lobes of the pituitary gland?
A
Anterior lobe (pars distalis) and posterior lobe (pars nervosa).
9
Q
How are the anterior and posterior pituitary connected to the hypothalamus?
A
Anterior: via portal blood vessels. Posterior: via nerve fibers from the hypothalamus.
10
Q
What hormones are released by the posterior pituitary?
A
Vasopressin (ADH) and oxytocin.
11
Q
What does vasopressin (ADH) do?
A
Acts on kidneys to reabsorb water, regulates blood osmolarity and urine output.
12
Q
What does oxytocin do?
A
Stimulates milk ejection and uterine contraction during labor.
13
Q
Where are posterior pituitary hormones produced?
A
In the paraventricular and supraoptic nuclei of the hypothalamus.
14
Q
What stimulates ADH release?
A
Increased plasma osmolarity due to hemorrhage or dehydration.
15
Q
How many hormones does the anterior pituitary secrete?
A
Six hormones.
16
Q
Name the six anterior pituitary hormones.
A
Growth hormone, prolactin, ACTH, TSH, FSH, LH.
17
Q
What is the function of anterior pituitary hormones?
A
Mostly tropic—regulate secretions of other endocrine organs.
18
Q
What triggers anterior pituitary hormone release?
A
Releasing hormones from the hypothalamus.
19
Q
Name 4 key hypothalamic releasing hormones.
A
CRH, TRH, GnRH, GHRH.
20
Q
What two hypothalamic hormones inhibit anterior pituitary activity?
A
Dopamine and somatostatin.
21
Q
What cells produce Growth Hormone (GH)?
A
Somatotrophs.
22
Q
What are the main targets of GH?
A
Bone and skeletal muscle.
23
Q
List 3 direct metabolic effects of GH.
A
Glucose sparing (anti-insulin), increased amino acid uptake, increased lipolysis.
24
Q
What hormone mediates indirect effects of GH?
A
Insulin-like Growth Factor (IGF).
25
What are IGF’s growth-promoting effects?
Soft tissue growth, skeletal growth, protein synthesis, cell proliferation.
26
What is ‘somatopause’?
Age-related decline in GH leading to decreased lean mass, bone density, and increased fat.
27
What factors stimulate GH release?
Stress, exercise, fasting, sleep, hypoglycemia, amino acids, sex hormones.
28
What causes gigantism?
GH excess during childhood before epiphyseal plate closure.
29
What is acromegaly?
GH excess in adults after epiphyseal plate closure, causing tissue overgrowth.
30
What features are associated with acromegaly?
Coarse facial features, enlarged hands/feet, jaw protrusion, deep voice, cardiomegaly, diabetes.
31
What is pituitary dwarfism?
GH deficiency in children with slow growth but normal proportions.
32
What are the symptoms of adult GH deficiency?
Usually no major symptoms.
33
Describe the speed and longevity of a steroid hormone
Slower, but more permanent
34
Describe the speed and longevity of a peptide hormone
Faster, but more temporary
35
Give 2 actions of oxytocin
Controls milk release from lactating breast
Controls uterine contraction at onset of
labour
36
What hormones does the posterior pituitary release?
Oxytocin
ADH
37
Give the pathway of the neuro-endocrine reflex
Suckling
Hypothalamus
Posterior pituitary
Oxytocin
Milk squeezed out
= Neuro-endocrine reflex
38
Describe the state of the collecting duct in the presence of ADH
Highly permeable to water, creates small volume of concentrated urine
39
Name the 6 tropic hormones created by the anterior pituitary
Growth Hormone
Prolactin
Adenocorticotropic hormone (ACTH)
Thyroid stimulating hormone (TSH)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
40
What kind of cell releases GH?
Somatotrophs
41
What kind of cell releases LH and FSH?
Gonadotrophs
42
What kind of cell releases ACTH?
Corticotrophs
43
What kind of cell releases TSH?
Thyrotrophs
44
What kind of cell releases prolactin?
lactotrophs
45
What stimulating hormones does the hypothalamus release?
Corticotrophin releasing hormone (CRH)
Gonadotropin releasing hormone (GRH)
Thyrotropin releasing hormone (TRH)
Growth hormone releasing hormone (GHRH)
46
Where is the thyroid gland located?
On the trachea, consists of two lobes connected by an isthmus
47
When is the thyroid gland fully developed in gestation?
By week 12
48
What is the functional unit of the thyroid gland? What is the basic structure of this functional unit?
The follicle, composed of follicular cells around a colloid-filled cavity.
49
Which two hormones does the thyroid primarily secrete?
Triiodothyronine (T3) and thyroxine (T4).
50
Which thyroid hormone is more biologically active?
T3 is 10x more active than T4.
51
How is thyroid hormone transported in plasma?
Bound to thyroxine-binding globulin or albumin
52
What are the raw materials for thyroid hormone synthesis?
Tyrosine (from thyroglobulin) and iodine.
53
What are MIT and DIT?
Monoiodotyrosine and diiodotyrosine – precursors for T3 and T4.
54
What enzyme is critical in thyroid hormone synthesis?
Thyroid peroxidase.
55
Where does T4 get converted to T3?
In peripheral tissues: liver, kidneys, skeletal muscle.
56
What is levothyroxine?
A synthetic hormone chemically identical to T4.
57
What are the major effects of thyroid hormones?
↑ Metabolism, oxygen consumption, glucose use, heart rate, temperature regulation.
58
How do thyroid hormones affect development?
They promote CNS development, growth, and work synergistically with GH.
59
What are additional systems affected by thyroid hormones?
Respiratory, skeletal muscle, reproduction, and sympathetic activity.
60
How is thyroid hormone secretion regulated?
Via hypothalamic-pituitary axis: TRH → TSH → T3/T4 with negative feedback.
61
What are the effects of TSH on the thyroid?
Stimulates hormone release, iodide pump, and iodination of tyrosines.
62
What triggers TRH release?
Low T3/T4 levels or environmental stress.
63
What are the primary effects of T3 and T4?
Regulate metabolic rate, growth, CNS development, and sympathetic activity.
64
What is hypothyroidism?
A condition of underactive thyroid resulting in decreased metabolism and weight gain.
65
What are common symptoms of hypothyroidism?
Dry skin, cold sensitivity, weight gain, memory impairment, lethargy.
66
How is hypothyroidism diagnosed and treated?
Low free T3/T4 in plasma
67
What are causes of hypothyroidism?
Iodine deficiency, autoimmune disease (e.g., Hashimoto’s), congenital defects, radiation, stress.
68
What is endemic goitre?
Thyroid enlargement due to iodine deficiency and high TSH stimulation.
69
What is Hashimoto’s thyroiditis?
Autoimmune thyroid disease where antibodies interfere with hormone synthesis and destroy the gland.
70
What is congenital hypothyroidism?
A birth defect resulting in intellectual disability and growth impairment (cretinism).
71
What are symptoms of congenital hypothyroidism?
Disproportionate body, thick tongue/neck, developmental delay.
72
What is hyperthyroidism?
Overactive thyroid with increased metabolism and weight loss.
73
Symptoms of hyperthyroidism?
Weight loss, heat intolerance, palpitations, anxiety, exophthalmos.
74
How is hyperthyroidism treated?
Surgery, radioactive iodine, or drugs that block T3/T4 synthesis.
75
What is the most common cause of hyperthyroidism?
Grave’s disease (autoimmune condition).
76
What is the mechanism of Graves' disease?
Autoantibodies mimic TSH, overstimulating the thyroid to release excess T3/T4.
77
What are key features of Graves' disease?
Goitre, exophthalmos, lid retraction, palpitations, irritability.
78
What is the basic structure of the thyroid gland?
Two lobes connected by an isthmus
79
What is the full name of T3?
Triiodothyronine
80
What is the full name of T4?
Thyroxine
81
How many atoms of iodine per molecule do T3 and T4 contain?
3
82
What are the 2 raw materials needed to produce T3 and T4?
Tyrosine
Iodine
83
What molecule provides tyrosine?
Thyroglobulin
84
In the colloid, what are linked together to form T3 and T4?
Iodinated tyrosines
85
What molecules form when tyrosine is combined with iodine in the colloid?
Monoiodotyrosine MIT
Diiodotyrosine DIT
86
90% of thyroid release is.....
T4
87
What hormone stimulates every aspect of thyroid function?
Thyroid stimulating hormone
88
What is the full name of TRH?
Thyro-trophin releasing hormone
89
Where are the adrenal glands located? What are they surrounded by?
On top of each kidney, surrounded by fat and a fibrous capsule.
90
What are the two parts of each adrenal gland?
Outer adrenal cortex and inner adrenal medulla.
91
What is the main function of the adrenal glands?
Respond to stress by secreting hormones; cortex and medulla function independently but share blood supply.
92
When does adrenal development begin?
At 7 weeks gestation; cortical zones fully differentiate in childhood.
93
What is the adrenal medulla derived from?
Specialized part of the sympathetic nervous system.
94
What cells make up the adrenal medulla?
Chromaffin cells (modified postganglionic neurons).
95
What hormones are secreted by the adrenal medulla?
Adrenaline (80%) and noradrenaline (20%).
96
What triggers adrenal medulla hormone release?
Acetylcholine from splanchnic nerve fibers.
97
What is the function of catecholamines?
Mediate the fight-or-flight response during acute stress.
98
Cardiovascular effects of adrenaline
↑ heart rate, stroke volume, BP; vasodilation in skeletal muscle; vasoconstriction in GIT/skin.
99
Respiratory and metabolic effects of adrenaline?
Bronchodilation; ↑ metabolic rate and glucose availability.
100
What types of receptors does adrenaline act on?
Alpha (α1, α2) and beta (β1, β2, β3), with major effects via beta receptors.
101
What are the three zones of the adrenal cortex and their hormones?
Zona glomerulosa – aldosterone (mineralocorticoid);
Zona fasciculata – cortisol (glucocorticoid); Zona reticularis – androgens.
102
What is the starting point of steroid hormone synthesis?
Cholesterol.
103
What is 21-hydroxylase deficiency associated with?
Genital ambiguity due to excessive androgen production.
104
What androgens are produced by the adrenal glands?
DHEA, DHEA-S, and androstenedione.
105
What controls adrenal androgen secretion?
ACTH from the anterior pituitary.
106
Effects of adrenal androgens in females?
Promote pubic/axillary hair, sex drive, and puberty initiation.
107
What can adrenal androgen excess cause in females?
Acne, hirsutism, irregular periods, breast shrinkage, PCOS.
108
What is DHEA-S and how does it change with age?
Weak androgen; most abundant hormone in young adults but declines with age.
109
What is aldosterone and where is it produced?
A mineralocorticoid produced in zona glomerulosa; essential for life.
110
How is aldosterone secretion regulated?
Primarily by the renin-angiotensin-aldosterone system (RAAS).
111
What are the key steps of RAAS activation?
↓ renal perfusion → renin → angiotensin I → (via ACE) → angiotensin II → aldosterone.
112
Main effects of aldosterone?
Sodium retention, potassium excretion, blood volume and pressure regulation.
113
What stimulates aldosterone release?
Low ECF volume, hypotension, low sodium, or high potassium.
114
What hormone must be present for aldosterone secretion, though it's not the primary stimulator?
ACTH.
115
Where is cortisol produced and what type of hormone is it?
Zona fasciculata; glucocorticoid.
116
What stimulates cortisol secretion?
Stress (physical, emotional, infection) and ACTH.
117
Main metabolic effects of cortisol?
↑ blood glucose, FFA, catabolism of muscle, gluconeogenesis, lipolysis.
118
What controls cortisol release?
CRH (hypothalamus) → ACTH (anterior pituitary) → cortisol (adrenal cortex).
119
How does cortisol act during stress?
Provides energy substrates and modulates immune and inflammatory responses.
120
What is Cushing’s syndrome?
Excess cortisol due to adrenal or pituitary tumor.
121
Symptoms of Cushing’s syndrome?
Muscle wasting, thin skin, central obesity, hyperglycemia, hypertension.
122
What is mineralocorticoid excess (e.g., Conn’s disease)?
Excess aldosterone → sodium retention, potassium loss, alkalosis, hypertension.
123
What is Addison’s disease?
Adrenal insufficiency due to autoimmune damage or pituitary failure.
124
Symptoms of Addison’s disease?
Fatigue, weight loss, skin pigmentation, electrolyte imbalance.
125
Why does Addison’s disease cause skin pigmentation?
Excess ACTH stimulates melanocytes due to similarity with MSH.
126
Which form of calcium is physiologically active?
Ionised/free calcium
127
What is the normal plasma calcium concentration?
2.2-2.6mM
128
What happens in hypocalcemia?
Neuronal hyperexcitability → tetany/muscle cramps
129
What happens in hypercalcemia?
Neuronal depression, kidney stones
130
What is the role of osteoclasts?
Bone resorption to release calcium.
131
What is the role of osteocytes?
Exchange of calcium between bone and extracellular fluid.
132
What are the types of calcium regulation?
Acute (plasma concentration) and chronic (total body calcium).
133
Where are the parathyroid glands located?
Behind the thyroid; ~4 small glands.
134
What hormone do parathyroid glands secrete?
Parathyroid hormone (PTH).
135
When is PTH secreted?
In response to low blood calcium.
136
What are the targets of PTH?
Kidney and bone (not directly the intestine).
137
What are the effects of PTH in the kidney?
Increases calcium reabsorption and phosphate excretion; activates 1α-hydroxylase.
138
What does PTH do in bone?
Increases osteoclast activity (indirectly) to resorb bone and release calcium.
139
How is PTH secretion regulated?
Negative feedback: high calcium and calcitriol inhibit secretion.
140
What does calcitriol do in the intestines?
Increases calcium absorption by upregulating calcium transport proteins.
141
What are calcitriol's effects on bone and kidney?
Increases bone resorption and mildly decreases calcium loss in urine.
142
Where is calcitonin secreted from?
Parafollicular (C) cells of the thyroid.
143
What are the effects of calcitonin?
Lowers calcium by inhibiting osteoclast activity and increasing urinary calcium/phosphate excretion.
144
Which hormones increase vs. decrease plasma calcium?
PTH and calcitriol increase; calcitonin decreases.
145
What 2 other hormones affect calcium balance?
Growth hormone, glucocorticoids
146
What is hyperparathyroidism?
Overproduction of PTH leading to hypercalcemia.
147
What is the main cause of hypocalcemia in children?.
Vitamin D deficiency
148
What is the adult version of rickets?
Osteomalacia – impaired bone mineralization due to Vitamin D deficiency.
149
Symptoms of hypocalcemia?
Tetany, muscle cramps
150
What causes Vitamin D deficiency?
Poor diet, low sunlight
151
What 3 ways is calcium found in blood plasma?
1) Protein-bound calcium
2) Ionized or free calcium
3) Complexed or chelated calcium
152
Explain how hypocalcemia causes tetany
Low ionized calcium levels in the extracellular fluid increases the permeability of neuronal membranes
to sodium ions
Causes a progressive depolarization,
which increases the possibility of
action potential
153
In order of importance, what 3 hormones control plasma calcium concentration?
1) Parathyroid hormone
2) 1,25-dihydroxycholecalciferol
3) Calcitonin
154
What are 2 other names for 1,25-dihydroxycholecalciferol?
Calcitriol
Activated vitamin D
155
What kind of hormone is PTH
Peptide
156
Where is PTH stored?
Within chief cells
157
When is PTH released?
In response to low blood calcium levels
158
What secretes calcitonin?
C-cells - parafollicular cells
159
What is the basic role of calcitonin?
Lowers the levels of free plasma calcium
160
What is CRH and what does it do?
Corticotropin-releasing hormone – stimulates ACTH release
161
What is TRH and what does it do?
Thyrotropin-releasing hormone – stimulates TSH and prolactin release
162
What is GnRH and what does it do?
Gonadotropin-releasing hormone – stimulates LH and FSH release
163
What is GHRH and what does it do?
Growth hormone-releasing hormone – stimulates GH release
164
What is ACTH and what does it do?
Adrenocorticotropic Hormone.
Stimulates the adrenal cortex, specifically the zona fasciculata, to produce and release cortisol.
Cortisol then helps regulate metabolism, the immune response, and stress response.
165
Describe somatotrophs
These are cells in the anterior pituitary.
They produce and secrete Growth Hormone (GH) in response to GHRH (Growth Hormone-Releasing Hormone) from the hypothalamus.
166
What is insulin-like growth factor 1 and what does it do?
Also known as somatomedin C.
Promotes cell growth, bone elongation, and tissue repair.
Provides negative feedback to the hypothalamus and pituitary to reduce GH and GHRH secretion.
167
What is somatostatin and what does it do?
Also called Growth Hormone-Inhibiting Hormone (GHIH).
Secreted by the hypothalamus.
Inhibits somatotrophs, reducing GH secretion
