CLINICAL ENDOCRINOLOGY Flashcards
Steroid hormones are synthesized from
Cholesterol
Amines are synthesized from
Tyrosine
Hormones behaving like steroids
Thyroid hormones
Behave like protein hormones
Cathecolamines
A releasing factor acts on the pituitary gland which in turn releases tropic hormones that act on a SPECIFIC TARGET gland ; stimulatory ; top-bottom
Positive feedback
Elevated levels of a target cell hormone TURN OFF the secretion of a stimulating hormone from the pituitary gland and a releasing hormone from the hypothalamus ; INHIBITORY Y; bottom to top
Negative feedback
Refers to the defect in the hypothalamus
Tertiary disorders
Refer to a defect in the anterior pituitary
Secondary disorders
Refer to a defect in the target organ
Primary disorders
Stimulates release of FSH, LH
Gonadotropin-releasing hormone
Stimulates release of ACTH
Corticotropin-releasing hormone
Stimulates release of TSH
Thyrotropin-releasing hormone
Stimulates release of growth hormone
GH-releasing hormone
Inhibits release of GH, TSH
Somatostatin
Inhibits release of Prolactin ; prolactin-inhibiting factor
Dopamine
Previously referred to as the master gland ; connected to the hypothalamus by infundibulum
Pituitary gland
Endocrine systems that are independent of the pituitary gland
RAAS, glucose-insulin axis, calcium-PTH axis
Anterior pituitary gland has 5 distinct populations of glandular cells
Somatotrophs
Lactotrophs
Thyrothrops
Gonadotrophs
Corticotrophs
Anterior Pituitary Glandular cell : secrete GH
Somatotrophs
Anterior Pituitary Glandular cell : secrete PRL
LACTOTROPHS
Anterior Pituitary Glandular cell : secrete TSH
Thyrotrophs
Anterior Pituitary Glandular cell : secrete FSH and LH
GONADOTROPHS
Anterior Pituitary Glandular cell : Secrete ACTH
Corticotrophs
Target tissue of FSH and LH
GONADS
Target tissue of ACTH
Adrenal cortex
Target tissue of TSH
Thyroid
Target tissue of prolactin
Breast
For follicle development ; secretion of estrogen ; sperm production
FSH
Stimulates ovulation and secretion of progesterone / testosterone
LH
Release of cortisol
ACTH
Release of cortisol
ACTH
Release of thyroid hormone
TSH
Production of milk
Prolactin
Growth of skeletal muscles and bones ; stimulates release of IGF-1 / somatomedin C
Growth hormone
Synthesized in the liver in response to stimulation by GH ; mediates the metabolic actions of GH ; negatively feeds back on the pituitary gland to inhibit GH secretion
IGF-1 / Somatomedin C
Clinical significance : FSH, LH, ACTH, TSH
SECONDARY HYYPO/HYPER SECRETION
Hypersecretion of GH in childhood
Gigantism
Hypersecretion of GH in adulthood
Acromegaly
Hyposecretion of GH in childhood
Dwarfism
Tropic hormones
FSH
LH
ACTH
TSH
General effectors
PRL & GH
Serves a repository of hormones produced by the SUPRAOPTIC and PARAVENTRICULAR NUCLEI of the hypothalamus, and releases them on demand
Posterior pituitary gland
ADH/AVP target tissue
Real tubules, arterioles
Clinical significance of ADH : Increased ADH
SIADH (Syndrome of inappropriate ADH secretion)
Clinical significance of ADH : decreased ADH
Diabetes melliltus
Preferred diagnostic test for identifying the presence of diabetes insipidus
Water-deprivation test
Diabetes insipidus type associated with lack of ADH production by the hypothalamus
Nephrogenic DI
Diabetes insipidus type associated with ADH presence but lacks renal response
Nephrogenic DI
_____ is a small butterfly shaped organ made up of 2 lobes that rest on each side of the trachea bridged by a band of tissue called ____
Thyroid gland ; isthmus
Follicles are superheroes of thyroid cells surrounding a core of a viscous substance termed ____ which mainly consists of ________, a glycoprotein manufactured exclusively by follicular cells
Colloid ; thyroglobulin
These cell produce T3 and T4 which are stored in the colloid of the follicles
Follicular cells
Produce calcitonin which is important in calcium homeostasis
Parafollicular cells
100% of thyroidal origin
T4
_____ - 20 of thyroidal origin ; 80% from _______ of T4 in nonthyroidal tissues
T3 ; monodeionization
70% of T4 is bound to _____ ; 20% bound to ________ : 10% bound to _______
Thyroxine binding globulin/TBG ; thyroxine binding prealbumin/transtyrethin ; albumin
0.04% of T4 and 0.4% of T3
Free forms
Hormones for regulation of oxygen consumption, heat production, growth, sexual maturity, and metabolism
Thyroxine (T4) ; 3,5,3’ - Triiodo-thyroxine (T3)
THYROXINE
T4
3,5,3’ - TRIIODO-THYRONIN
T3
CLINICAL SIGNIFICANCE : primary hyperthyroidism
Grave’s disease, T3 thyrotoxicosis
Clinical significance : primary hypothyroidism
Hashimoto’s congenital hypothyroidism (cretinism)
Reverse T3
3,3,5’ - TRIIODO-THYRONINE
Clinical significance : increased reverse T3
Non-thyroidal illness / erythroid sick syndrome
Regulation of calcium
Calcitonin
Calcitonin clinical significance
Medullary thyroid carcinoma
Tumor marker for medullary thyroid carcinoma
Calcitonin
Most important test of thyroid function
TSH
Biologically active form of T4
FT4
FT4 requires separation of the hormone from its carrier protein using _________
Equilibrium dialysis
Reflects the quantity of TBG present and the quantity of hormone attached to it
T3 uptake
Relative estimate of free T4 concentration ; product of Total T4 and Thyroid hormone binding ratio (THBR)
FTI (FREE T4 INDEX)
FREE T4 INDEX FORMULA
FTI - TT4 X (Px T3 uptake / mean normal T3 uptake)
Biologically active form of T3
FT3
T3 is only tested when TSH is ___ and T4 is ____
Low ; normal
____ - measures thyroidal uptake of radioactive iodine after an oral dose of _____ ; useful in the evaluation and treatment of thyroid cancer
Radioactive iodine uptake ; iodine-131
____ - Detected as thyroid microsomal antibodies using agglutination or immunofluorescence ; very sensitive marker for __________
Anti-TPO ; Hashimoto’s thyroiditis
Thyroid-stimulating antibodies that mimic the action of TSH
TRAb / TSHRAb
TRAb / TSHRAb is positive in 85% of patients with ______
Graves diseae
Primary hyperthyroidism
TSH
FT4
Total T4/T3
T3uptake
⬇️
⬆️
⬆️
⬆️
Primary hypothyroidism
TSH
FT4
Total T4/T3
T3uptake
⬆️
⬇️
⬇️
⬇️
Secondary hyperthyroidism
TSH
FT4
Total T4/T3
T3uptake
⬆️
⬆️
⬆️
⬆️
Secondary hypothyroidism
TSH
FT4
Total T4/T3
T3uptake
⬇️
⬇️
⬇️
⬇️
Euthyroid with abnormally high TBG
TSH
FT4
Total T4/T3
T3uptake
N
N
⬆️
⬇️
Euthyroid with abnormally Low TBG
TSH
FT4
Total T4/T3
T3uptake
N
N
⬇️
⬆️
Tissue source of aldosterone (mineralocorticoid)
Zona glomerulosa
Tissue target of aldosterone (mineralocorticoid)
Kidneys
For blood pressure and electrolyte regulation (under the control of RAAS)
ALDOSTERONE
Tissue source of cortisol
Zona fasciculata
Tissue target of cortisol
General
For carbohydrate, protein, and lipid metabolism
Cortisol
Tissue source of sex steroids
Zona reticularis
Tissue target of sex steroids
Gonads, muscles, and bones
Precursor to active androgens ; growth and maturation
Sex steroids
Tissue source of epinephrine and norepinephrine
Medulla
Stimulates sympathetic nerves ; promotes glycogenolysis and lipolysis
Epinephrine
Stimulates sympathetic nerves
Norepinephrine
Tissue target of epinephrine
Sympathetic nerves, liver, skeletal muscle, and adipose
Tissue target of epinephrine
Sympathetic nerves, liver, skeletal muscle, and adipose
Synthesis and metabolism of cathecolamines (order)
Tyrosine
L-3,4-dihydroxyphenylalanine
Dopamine
Norepinephrine
Epinephrine
“TRUE LOVE DOES NOT EXIST”
Dopamine is further metabolized into
Homovanilic acid
Norepinephrine is further metabolized into
Normetanephrine
Epinephrine is further metabolized into
Metanephrine
Normetanephrine and metanephrine are further metabolized into
vanillylmandelic acid
Plasma ACTH requires the use of _____
Pre chilled tubes
Cushing syndrome
Plasma cortisol:
Plasma ACTH :
High dose of dexamethasone :
⬆️
⬇️
no
Primary hypercorticolism (Target organ defect)
Cushing disease
Plasma cortisol:
Plasma ACTH :
High dose of dexamethasone :
⬆️
⬆️
yes
Secondary hypercorticolism (defect sa anterior pituitary)
Ectopic CS (ACTH producing tumor)
Plasma cortisol
Plasma ACTH
HD-DST
Markedly increased
Markedly increased
Usually not suppressed
Urinary potassium secretion, captopril suppression, upright PA/PRA ratio, 18-hydroxycorticosterone
Tests for primary aldosteronism (Conn’s disease)
Urine free cortisol collected over 24 hours, midnight salivary cortisol, dexamethasone suppression test , plasma ACTH
Cushing’s syndrome / disease
Urine free cortisol collected over 24 hours, midnight salivary cortisol, dexamethasone suppression test , plasma ACTH
Cushing’s syndrome / disease
ACTH stimulation (Cortrosyn) test, insulin tolerance test, metyrapone test
Addison’s disease tests
21-hydroxylase, plasma 17-hydroxyprogesterone and prenanetriol, urinary pregnanetriol and keto steroids
Congenital adrenal hyperplasia tests
Development of overt male secondary sexual features
Virilization
Non typically appearing female external female genitalia
General ambiguity
Excessive hair growth due to increased ovarian androgens in women
Hirsutism
Scales used for grading hirsutism
Ferriman-Gallwey scale
Contain germ cells and Sertoli cells
Seminiferous tubules
Contains Leydig cells
Interstitium
Synthesize testosterone
Leydig cells
Principal androgen synthesized in the testes (95%); <5% derived from adrenal precursors ;
Testosterone
Testosterone bound to albumin (%)
50%
Testosterone bound to Sex hormone-binding globulin (SHBG)(%)
45%
Testosterones metabolites
Estradiol, Dihydrotestosterone
MALE GONADAL
Primary Hypergonadism
Other name:
FSH, LH :
Testosterone
Testicular tumor
⬇️
⬆️
MALE GONADAL
Primary Hypogonadism
Other name:
FSH, LH :
Testosterone
Klinefelter syndrome (47, XXY)
⬆️
⬇️
MALE GONADAL
Secondary Hypergonadism
Other name:
FSH, LH :
Testosterone
Precocious puberty
⬆️
⬆️
MALE GONADAL
Secondary Hypogonadism
Other name:
FSH, LH :
Testosterone
Panhypopituitarism
⬇️
⬇️
OVARIES :
Approximately 400,000 in neonates, each containing an immature ovum
Primordial follicles
OVARIES :
_____ - Selected from a cohort of follicles ; releases ovum during the luteal phase giving rise to ______
Dominant Graofian follicle ; corpus luteum
PLACENTA :
Vascular projections of fetal tissue surrounded by chorion
Chorionic villi
PLACENTA :
Vascular projections of fetal tissue surrounded by chorion
Chorionic villi
Consist of syncytiotrophoblast which is in direct contact with maternal blood, and the inner cytotrophoblast
Chorion
Consist of syncytiotrophoblast which is in direct contact with maternal blood, and the inner cytotrophoblast
Chorion
Principal and most potent estrogen in premenopausal women
Estradiol (E2)
Metabolite of estradiol or produced form androstenedione
Estrone (E1)
Produced by the ovaries and the placenta
Estriol (E3)
Androstenedione, dehydroandrostenedione, testosterone, and DHT
Androgens
Chief female androgens ; produced by the corpus luteum and the placenta ; prepare the endometrium for implantation and maintains pregnancy
Progesterone
Structurally similar to prolactin and growth hormone ; stimulates development of mammary gland ; increases maternal plasma glucose levels
hPL
Produced by the syncyctiotrophoblast cells of the placenta ; stimulates the ovary to produce progesterone which in turn prevents menstruation
hCG
HCG dimeric hormone Same as FSH, LH, TSH
hCG alpha subunit
HCG dimeric hormone : Unique ; confers antigenic individuality
hCG Beta subunit
Increases from <5 mIU /mL to >100,000 mIU/mL ; peak at about 16 weeks of gestation
HCG
Ovarian tumor
Primary hypergonadism
Menopause or Turner syndrome (44X)
Primary Hypogonadism
Gonadotropin-secreting tumors
Secondary hypergonadism
Sheehan’s syndrome
Secondary Hypogonadism
Tissue source of melatonin
Pineal gland
Tissue target of melatonin
Hypothalamus
Tissue source of serotonin
Pineal gland and GIT
Tissue target of serotonin
Cardiovascular, respiratory, and gastrointestinal systems, brain
Neurotransmitters, stimulation or inhibition of various smooth muscles and nerves
Serotonin
Serotonin clinical significance : high serotonin
High in the blood (argentaffinoma/carcinoid syndrome)
High in urine (5-HIAA)
Gastrin tissue source
GIT
Gastrin tissue target
Stomach
Secretion of gastric acid, gastric mucosal growth
Gastrin
Clinical significance : high Gastrin
Zollinger-Ellis syndrome (gastrinoma)
Tissue source of adiponectin and leptin
Adipose
Tissue target of adiponectin
Muscle, liver
Tissue target of leptin
Hypothalamu s
Increases fatty acid oxidation ; suppresses glucose formation
Adiponectin
Inhibition of appetite ; stimulation of metabolism
Leptin
Adiponectin and leptin clinical significance : low
Metabolic syndrome
