L1 Introduction to Endocrinology Flashcards Preview

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Flashcards in L1 Introduction to Endocrinology Deck (20):
1

Properties of Steroid Hormones

- No storage pools
- Diffuse through cell membrane
- Receptor is in cytoplasm or nucleus
- Acts to regulate gene transcription
- Response time: hours to days

2

Properties of Peptide Amine Hormones

- Stored in secretory vesicles
- Bind to receptors on cell membrane
- Acts via signal-transduction cascade to affect many cell processes
- Response time: seconds to minues

3

Pseudohypoparathyroidism

- Defect: alpha subunit of G protein --> impairs ability of PTH to regulate body calcium and phosphorus
- Pts have low serum [Ca2+] and high serum phosphate levels
- Pseudo because pts have high circulating levels of PTH, it just can't act normally on target tissue

4

What are the hormones released by the anterior pituitary?

FLAT PiG
- FSH
- LH
- ACTH
- TSH
- PRL (prolactin)
- GH

5

Growth hormone

- Hypothalmic releasing factor: GHRH (inhibitied by somatostatin)
- GHRH targets somatotroph cells in anterior pituitary
- GH is released by anterior pituitary
- Targets multiple somatic tissues

6

TSH (Thyroid stimulating hormone)

- Hypothalmic releasing factor: TRH
- TRH targets thyrotroph cells in anterior pituitary
- TSH is released by anterior pituitary
- Targets thyroid foliuclar cells, stimulated to make thyroid hormone

7

ACTH (adrenocorticotrophic hormone)

- Hypothalmic releasing factor: CRH (corticotrophin-releasing hormone)
- CRH targets corticotroph cells in anterior pituitary
- ACTH is released by anterior pituitary
- Targets fasiculata and reticularis cells of the adrenal cortex to make corticosteroids

8

FSH

- Hypothalmic releasing factor: GnRH (gonadotrophin releasing factor)
- GnRH targets Gonadotroph cells in anterior pituitary
- FSH is released by anterior pituitary
- Targets ovarian follicular cells to make estrogen and progestins, targets Sertoli cells to initiate spermatogensis

9

LH

- Hypothalmic releasing factor: GnRH (gonadotrophin releasing factor)
- GnRH targets Gonadotroph cells in anterior pituitary
- LH is released by anterior pituitary
- Targets ovarian follicular cells to make estrogen and progestins, targets Leydig cells to make testosterone

10

Prolactin (PRL)

- Under tonic inhibitory control by dopamine
- TRH stimulates prolactin release
- Target cell in anterior pituitary: lactotroph cells
- PRL is released by anterior pituitary
- Negative feedback on itself by enhancing DA release (short-loop pathway)
- Targets mammary glands, initiates and maintains milk production. Also promotes breast development during puberty and inhibits ovulation

11

How is excessive prolactin secretion (hyperprolactinemia) treated?

With a dopamine receptor agonist (i.e. bromocriptine)
- Note circulating prolactin increases if pituitary stalk is severed or a pt is taking a DA receptor antagonist

12

Oxytocin

- Synthesized and released in posterior pituitary (paraventricular nuclei)
- Targets uterus (for contractions) and breasts to stimulate milk ejection
- Can also be released in response to sight, smell, or sound of an infant, and orgasm

13

Vasopressin (ADH)

- Synthesized and released in posterior pituitary (mainly in supraoptic nuclei, some in paraventricular nuclei)
- Main fx is water balance
- Released in response to increased osmolarity of extracellular fluid and decreased BO
- Targets collecting duct to increase water permeability/reabsorption by kidney
- High plasma ADH levels --> low volume of concentrated urine

14

What causes central diabetes insipidus? What do patients present with?

- Caused by failure of the posterior pituitary to secrete ADH
- Affected pts produce large amounts of dilute urine, body fluids become concentrated

15

What is hypopituitarism?

- Inability of the pituitary gland to produce hormones or an insufficiency of hypothalamic-releasing hormones
- Most common cause (classically) is pituitary tumor
- Also caused by brain damage
- Pts with TBI or subarachnoid hemorrhage are at high risk

16

Symptoms and findings of corticotropin deficiency

- Chronic: fatigue, pallot, anorexia, weight loss (findings: hypoglycemia, hypotensions, anaemia, lymphocytosis, eosiniphilia, hyponatraemia)
- Acute: weakness, dizziness, nausea/vomiting, circulatory collapse, fever, shock
- Children: delayed puberty, failure to thrive

17

Symptoms and findings of thyrotropin deficiency

- General symptoms: tiredness, cold intolerance, constipation, hair loss, dry skin, hoarseness, cognitive slowing
- Findings: weight gain, bradycardia, hypotension
- Children: retarded development, growth retardation

18

Symptoms and findings of gonadotropin deficiency

- Women: oligoarnenorrhea, loss of libido, dyspareunia, infertility (finding: osteoporosis)
- Men: loss of libido, impaired sexual fx, mood impairment, loss of facial/scrotal/trunk hair (finding: decreased muscle mass, osteroporosis, anaemia)
- Children: delayed puberty

19

Symptoms and findings of growth hormone deficiency

General symptoms: decreased muscle mass and strength, visceral obesity, fatigue, decreased quality of life, impairment of attention and memory (findings: dyslipidaemia, premature arteriosclerosis)
- Children: growth retardation

20

Symptoms and findings of antidiuretic hormone deficiency

- Polyuria, polydipsia
- Findings: decreased urine osmolality, hypernatraemia, polyuria