E1 - Introduction to endocrinology and diseases of the pituitary Flashcards
1
Q
What is a hormone?
A
- a signaling molecule that travels from the site of production to exert actions on a different site
- endocrine hormones travel via the blood
2
Q
What are the main types of hormones?
A
- simple molecules: such as amino acids (ie. thyroid hormones, adrenal catecholamines)
- steroids: produced by adrenal cortex or gonads (testicles/ovaries), vitamin D
- peptides (ie. TRH)
- complex proteins (ie. pituitary hormones)
3
Q
What are the hormone producing organs?
A
- pituitary
- heart
- liver
- lungs
- kidney
- thyroid and parathyroids
- adrenal gland
- ovary
- testicle
- pancreas
4
Q
What are the processes regulated by hormones?
A
- maintenance of homeostasis
- adaptation to internal/external circumstances
- regulation of metabolism
- growth and development
- several other physiological processes (ie. heart/bowel functioning, blood pressure etc.)
5
Q
What are the pituitary hormones?
A
- prolactin
- growth hormone
- ADH
- oxytocin
6
Q
What are the main actions of prolactin?
A
- stimulation of milk production in women
- inhibits LH/FSH secretion from pituitary
- inhibited by hypothalamic dopamine
7
Q
What are the main actions of growth hormone?
A
- direct effects and via IGF-1 secretion
- cell proliferation, growth promotion, increases blood glucose levels
8
Q
What are the main actions of ADH?
A
- antidiuretic hormone
- acts on AVP2 receptors to increase water reabsorption from kidney collecting channels
- acts on AVP1 as the most potent vasoconstrictor
9
Q
What are the main actions of oxytocin?
A
- uterus contraction, lactation
- social behavior and socialisation
- no diseases related to overproduction
10
Q
What are the two main hormones of the thyroid?
A
- T3: active thyroid hormone that is capable of binding to receptor
- T4: is produced in larger quantities
11
Q
What is the importance of thyroid hormones?
A
- development of CNS and heart
- major regulators of metabolic functions
- overproduction leads to weight loss, tachycardia, increased bowel movements, subfebrility, and hyperactivity
12
Q
Conversion of T4 to T3
A
- takes place in peripheral organs
- regulated by deiodinase enzymes (selenoproteins)
- T4 is stored in colloid bound by thyroglobulin
- Na-I symporter on basolateral membrane of the thyrocyte and thyroid peroxidase (TPO) on apical membrane are important for thyroid hormone production
13
Q
What is calcitonin?
A
- produced by thyroid C-cells (part of neuroendocrine system)
- regulates Ca metabolism (reduces blood Ca)
- total thyroidectomy does not result in increased Ca, and high levels of calcitonin does not cause low Ca (relevance in humans is unclear)
14
Q
What are the parathyroids?
A
- 4 glands localized behind the thyroid but can occur ectopically
- secretion of PTH is regulated by calcium censors on the parathyroid cell membrane
15
Q
What are the actions of parathyroid hormone?
A
- stimulates osteoclast activity (calcium release from the bone)
- stimulates 1α-hydroxylation of vitamin D and calcium reabsorption from the kidney
- increases blood Ca
16
Q
What are the effects of vitamin D?
A
- calcium reabsorption from the intestines
- calcium deposition in the bone
- immunological and antitumor activities
17
Q
Histology of the adrenal gland
A
- adrenal cortex
- zona granulosa
- zona fasiculata
- zona reticularis - adrenal medulla
18
Q
What are the adrenocortical hormones?
A
- glucocorticoids
- mineralocorticoids
- adrenocortical androgens
19
Q
What are the effects of glucocorticoids?
A
- produced by the zona fasiculata
- regulators of metabolism: increases glucose formation and release, increased blood glucose
- stimulates protein and fat degradation (catabolic hormone)
- inhibits bone formation, stimulates bone degradation
- suppresses inflammatory responses
20
Q
What are the effects of mineralocorticoids?
A
- produced by the zona glomerulosa
- regulation of salt and water homeostasis
- stimulates Na reabsorption
- stimulates potassium and hydrogen release
- a main regulator of blood pressure
21
Q
What are the effects of adrenocortical androgens?
A
- produced by zona reticularis
- DHEAs produced in largest quantity
- sex hormones for secondary sexual development (ie. estrogen and testosterone)
22
Q
How are the adrenocortical hormones regulated?
A
- hypothalamus produces CRH (corticotropin releasing hormone)
- pituitary produces ACTH (adrenocorticotropic hormone) upon CRH stimulation
- ACTH then stimulates the production of hormones in the adrenal gland
- adrenocortical hormones (ie. cortisol) act on the hypothalamus and pituitary to send negative feedback
23
Q
What are the catecholamines?
A
- adrenaline and noradrenaline (epinephrine, norepinephrine)
- produced by the adrenal medulla (adrenaline is only produced by adrenals, but noradrenaline can also be produced by neurons)
- they act as neurotransmitters that are mediators of vegetative nervous system
- pheochromocytoma: overproduction of catecholamines leading to increased heart rate, blood pressure, severe cardiovascular complications
- no effects in case of catecholamine deficiency
24
Q
How is the production of sex hormones regulated?
A
- pulsatile secretion of GnRH regulates the secretion of LH and FSH
- inhibin is produced by the gonads for negative feedback
- activin is part of a positive autoregulatory loop
25
Q
What are the secondary sex characteristics?
A
- developments at puberty
- breast development in women
- voice deepening in men
- development of muscles and sexual hair in both
- estrogen (esp. estradiol) is important in women and testosterone in men
26
Q
What are the primary sex characteristics?
A
- development of the gonads
- ovaries in women
- testicles in men
27
Q
What are some clinical effects of abnormal sex hormone levels?
A
- amenorrhea:
- primary: no menstrual cycles until the age of 16 yrs
- secondary: reached menstruation (regular cycles for min. 3 months) and then stopped (irregular menses for 6 months) - oligomenorrhea: decreased frequency of menses
- galactorrhea: lactation in non-suckling women
- hirsutism: increased body hair in androgen dependent regions
- hypertrichosis: increased hair in non androgen-dependent regions
28
Q
What is primary insufficiency?
A
- disease of the peripheral hormone producing organ
- peripheral hormone is low, pituitary hormone is high
29
Q
What is secondary insufficiency?
A
- lack of pituitary frontal lobe hormones
- peripheral hormones are low along with pituitary hormones
30
Q
What is tertiary insufficiency?
A
- lack of hypothalamic trophormones, so all hormone levels are low
31
Q
What are the main forms of hormone diseases?
A
-
hormone deficiency:
- developmental disorder of endocrine glands
- autoimmune damage
- lack of substance needed for hormone production -
disturbance of hormone action:
- hormone resistance -
hormone overproduction:
- hormone-producing tumors
- due to autoimmune diseases -
endocrine tumors w/o hormone production
- hormonally inactive
32
Q
What are the tumors of neuroendocrine organs?
A
- pituitary neuroendocrine tumor
- adrenal medulla (pheochromocytoma)
- parathyroid glands
- thyroid C-cells (medullary thyroid cancer)
33
Q
What tumors originate from dispersed neuroendocrine cells?
A
- originate from formerly carcinoid tumors
- mostly in GI system
- neuroendocrine tumors of respiratory tract
34
Q
What is paraneoplastic syndrome?
A
- tumor secretes a soluble mediator or induces an immune reaction affecting tissues and organs distant from the tumor (not based on size, invasion or metastasis of tumor)
- 8% of all malignant tumors
35
Q
What can cause hypothalamic dysfunction?
A
- tumors
- bleedings
- developmental abnormalities
- granulomatous inflammation
- inflammation
- trauma
- irradiation
- inherited diseases
36
Q
What are the diseases of the hypothalamus?
A
- lack of trophic hormones (CRH, TRH, GnRH, GHRH) leading to growth delay, hypopituitarism or disorders of sexual development
- deficiency of posterior pituitary hormones
- non-endocrine consequences of hypothalamic disorders: appetite problems, liquid homeostasis disorders, thermal regulation disorders, somnolecence, coma or mood problems
