2S [LEC]: Endocrinology 2 [hypothalamus & thyroid] Flashcards
Hormones that can increase prolactin production
Thyroid-releasing hormone
Prolactin-releasing hormone
A small region in the brain that plays a crucial role in maintaining homeostasis by regulating various bodily functions through its control over the endocrine system and autonomic nervous system
Hypothalamus
The “master gland”
Pituitary gland
This hormone is released in the blood and circulates to the hypothalamus and pituitary to suppress further TRH and TSH production
Thyroxine
Other name for growth hormone
Somatotropin
A hormone that is structurally related to prolactin and human placental lactogen
Growth hormone
Growth hormone is classified as a ___ hormone
Trophic
The tropic function of the growth hormone is that it acts on the liver to produce ___
Insulin-like growth factor 1/ Somatomedin C
Hormone that regulates the somatotropin
Somatostatin
An inhibitory hormone produced both in the hypothalamus and pancreas, regulating somatotropin and TSH
Somatostatin
A hormone produced by the pituitary gland that plays a crucial role in reproductive health by stimulating the growth and development of ovarian follicles in females and sperm production
Follicle-stimulating hormone
Processes in the body that regulate hormone secretion
Feedback Mechanisms
“Controlled Defiance”
Negative feedback loop
“Controlled Amplification”
Positive feedback loop
A feedback loop that regulates thyroid hormone production through interactions between the hypothalamus, pituitary gland, and thyroid gland
Hypothalamic-Pituitary-Thyroid Axis
The natural process by which a pregnant mammal gives birth, involving the contractions of the uterus to expel the fetus and placenta
Parturition
Hormone responsible for parturition
Prolactin
Type of feedback mechanism:
Feedback from hormones produced in the pituitary target glands on the hypothalamus
Long feedback mechanism
Type of feedback mechanism:
Feedback of hormones at the level of the pituitary gland
Short feedback mechanism
Type of feedback mechanism:
Feedback between the pituitary and hypothalamus
Ultrashort feedback mechanism
Precursor of ACTH and melanocyte-stimulating hormone, playing roles in stress response, pigmentation, and energy balance
Proopiomelanocortin
FSH is produced in the ___
Anterior pituitary gland
A hormone pivotal in both male and female reproductive systems, where it stimulates testosterone production in the testes of males and triggers ovulation and progesterone secretion in females
Luteinizing Hormone (LH)
Growth hormone is produced in the ___
Anterior pituitary gland
Effect of sleep on growth hormone production
Increase
Effect of exercise on growth hormone production
Increase
Effect of fasting on growth hormone production
Increase
Effect of hyperglycemia on growth hormone production
Decrease
Effect of increased somatomedin C on growth hormone production
Decrease
Effect of insulin deficiency on growth hormone production
Decrease
FSH acts on the ___ for sperm production
Seminiferous tubule
Hormone that acts on ovarian follicle to produce estrogen and progesterone and Leydig cells for testosterone production
Luteinizing hormone
The ___ produces testosterone as a response to LH
Leydig cells
ACTH is ___ in the morning
High
Hormone produced in the anterior pituitary gland that stimulates adrenal glands to release cortisol, in response to stress and low blood glucose levels
Adrenocorticotropic hormone
In ACTH determination, which tube is preferred?
Plastic tube (ACTH adheres to glass surfaces)
Effect of glass tube in ACTH determination
False decrease
Transportation consideration of an ACTH specimen
Chilled in an EDTA anticoagulant
Cushing’s syndrome is classified as ___ hypercortisolism
Primary
Cushing’s disease is classified as ___ hypercortisolism
Secondary
Classify the hypercortisolism:
Increased cortisol
Decreased ACTH
Decreased Corticotropin releasing hormone
Primary
Classify the hypercortisolism:
Increased cortisol
Increased ACTH
Decreased Corticotropin releasing hormone
Secondary
Classify the hypercortisolism:
Increased cortisol
Increased ACTH
Increased Corticotropin releasing hormone
Tertiary
Early stage of hyperthyroidism with normal T3 and T4 but decreased TSH
Subclinical hyperthyroidism
Grave’s disease is classified as ___ hyperthyroidism
Primary
Hormone secreted by the pituitary gland that stimulates milk production in the mammary glands of mammals, typically rising during pregnancy and breastfeeding, promoting lactation
Prolactin
Major inhibitor of prolactin
Dopamine
T/F: Excess prolactin can cause hypergonadism
False (it causes hypogonadism)
Feedback hormone for growth hormone
Somatomedin C
Feedback hormone for FSH
Inhibin
Feedback hormone for ACTH
Cortisol
Feedback hormone for TSH
T3/ T4
Feedback hormone for prolactin
Unknown
Target gland of FSH and LH
Gonads
Target gland of ACTH
Adrenal cortex
Target gland of TSH
Thyroid
Target gland of prolactin
Breast
A neuroendocrine reflex, a self-sustaining cycle of uterine contractions, initiated by pressure on the cervix or vaginal walls, leading to the release of oxytocin and further contractions, ultimately aiding in childbirth
Ferguson reflex
A hormone that maintains osmotic homeostasis by regulating water balance
Arginine vasopressin (AVP) or Pitressin
A potent stimuli to ADH release
Emetic (dehydration)
Inhibitors of ADH release
Ethanol, cortisol
A medical condition characterized by inadequate production of growth hormone by the pituitary gland, leading to impaired growth and development in children and metabolic abnormalities in adults
Growth hormone deficiency
Most common cause of growth hormone deficiency
GHRH gene mutation
Hyposecretion of GH during growth years
Dwarfism
Type of dwarfism that is due to genetic cause and results to abnormal bone growth
Disproportionate dwarfism
Type of dwarfism caused by metabolic abnormalities
Proportionate dwarfism
Most common type of disproportionate dwarfism
Achrondoplasia
Tallest among the dwarfism cases
Hypoachondroplasia
Most rare case of dwarfism wherein the abnormality is present in the fetal stage
Spondyloepiphyseal Dysplasia Congenita (SEDC)
Most disabling dwarfism case, causing limb deformity
Diastrophic dysplasia
This condition results from overproduction of growth hormone by the pituitary gland, often due to a tumor
GH Excess
Most common cause of GH excess
Pituitary tumor
Aside from pituitary tumor, this is also a cause of GH excess, which increases the risk of an individual to develop pituitary adenoma
AIP (aryl hydrocarbon receptor [AhR] interaction protein) gene mutation
Hypersecretion of GH during childhood
Gigantism
Hypersecretion of GH during adulthood
Acromegaly
Characterized by coarse facial features, spade like hands, protruding jaw
Acromegaly
T/F: Acromegaly can cause impaired glucose tolerance or DM
True
A pituitary tumor that directly secretes prolactin, and it represents the most common type of pituitary tumor
Prolactinoma
Can cause galactorrhea, amenorrhea, and impotance
Prolactinoma
An excessive secretion of ACTH, causing round, puffy face, buffalo hump, and abnormal obesity with thin limbs
Cushing’s disease
Level of aldosterone in Cushing’s disease
Decreased
Level of renin in Cushing’s disease
Decreased
Level of cortisol in Cushing’s disease
Increased
Best time to collect specimen for cortisol determination
Morning
Postpartum hypopituitarism caused by necrosis of the pituitary gland
Sheehan’s syndrome
Hypopituitarism caused by severe hypotension or shock caused by massive hemorrhage during or after delivery
Sheehan’s syndrome
Osmolality that secretes ADH, indicating dehyration
> 295 mOsm/kg
Osmolality that suppresses the secretion of ADH, indicating hydrated state
<284 mOsm/kg
A type of diabetes insipidus wherein there is a faulty thirst hypothalamic mechanism, causing excessive water intake
Primary polydipsia/ Dipsogenic DI/ Psychogenic polydipsia
DI caused by enzymatic breakdown of the endogenous AVP by a placental cysteine aminopeptidase
Gestational DI
Specific gravity of urine in DI
<1.002
A primary polydipsia wherein the setpoint for ADH secretion is normal, but a resetting of the thirst threshold occurs so that it is now below the threshold for ADH secretion
Dipsogenic DI
A primary polydipsia wherein the osmostat for ADH secretion is normal
Psychogenic polydipsia
A gland positioned lower anterior neck and shaped like a butterfly
Thyroid gland
The thyroid gland rests on the trachea and is bridged by the ___
Isthmus
Structural unit of thyroid gland
Follicle
Cells in the thyroid gland producing T3 and T4
Follicular cells
Follicular cells are made up of ___
Colloid cells
Colloid cells are made up of ___
Thyroglobulin
The gelatinous, PAS-positive material in the thyroid gland
Colloid cells
Parafollicular cells are also called ___
C cells
Hormone secreted by the parafollicular cells of the thyroid gland
Calcitonin
Hormone that suppresses calcium release
Calcitonin
These hormones influence nearly every organ system, impacting processes ranging from heart rate and body temperature to digestion and energy expenditure
Thyroid hormones
The amino acid precursor of thyroid hormones
Tyrosine
The iodination of tyrosine is done by which enzyme?
Thyroid peroxidase
Components of the T3
1 monoiodothyrosine
1 diiodothyrosine
Components of the T4
2 diiodothyrosine
This hormone signals the follicular cells to ingest a microscopic droplet of colloid by endocytosis
TSH/ Thyrotropin
The primary cause of hypothyroidism used to be ___
Iodine deficiency
The principal secretory product of thyroid hormone
T4
The prehormone for T3 production
T4
The metabolically active thyroid hormone
T3
The major product of the tissue deiodination of T4
T3
The better thyroid hormone that indicates recovery from hyperthyroidism
T3
How many percent of the T3 is the product of the deiodination of T4?
80%
The difference between T3 and rT3 is that the deiodination occurs in the ___ in T3 and ___ in rT3
T3: Outer ring
rT3: Inner ring
Biologically inactive form of thyroid hormone
rT3
3rd major circulating thyroid hormone
rT3
The enzyme responsible in the removal of iodine from T4 for it to be converted into T3
Iodothyronine 5-deiodinase (type 1 & type 2)
The more abundant iodothyronine 5-deiodinase type
Type 1
The source of type 1 iodothyronine 5-deiodinase
Kidneys
Liver
Source of type 2 iodothyronine 5-deiodinase
Brain
Pituitary gland
How many percent of T3 are unbound to proteins?
0.4%
How many percent of T4 are unbound to proteins?
0.04%
Carrier molecules in the bloodstream that transport thyroid hormones, ensuring their stability and distribution throughout the body
Major binding protein
The major transporter protein of thyroid hormones
Thyroxine binding globulin (TGB)
A condition characterized by excessive production of thyroid hormones, typically resulting from an overactive thyroid gland
Hyperthyroidism
Grave’s disease causes hyperthyroidism due to the production of autoantibodies called ___
Thyroid stimulating immunoglobulins (TSIs)
These antibodies mimic the action of TSH and bind to the receptor on thyroid follicular cells
Thyroid stimulating immunoglobulins (TSIs)
Most common case of thyrotoxicosis
Grave’s disease
Symptoms may include weight loss, rapid heart rate, anxiety, tremors, and heat intolerance
Hyperthyroidism
A condition marked by an underactive thyroid gland, resulting in insufficient production of thyroid hormones
Hypothyroidism
Symptoms may include fatigue, weight gain, cold intolerance, dry skin, and constipation
Hypothyroidism
Most common case of hypothyroidism
Hashimoto’s thyroiditis
Antibodies that may be present in Hashimoto’s thyroiditis
Anti-thyroid peroxidase
Anti-thyroglobulin
A glycoprotein produced by the thyroid gland that is an essential in T3 and T4 production
Thyroglobulin
Most common case of thyroiditis, causing leakage of thyroid hormone and resulting to hypothyroidism
Postpartum thyroiditis
An anti-arrhythmic medication medication that has a high iodine content, inhibiting thyroid hormone release and therefore causing hypothyroidism to patients
Amiodarone
The phenomenon where high iodine content inhibits the release of thyroid hormone release as part of the negative feedback mechanism
Wolff-Chaikoff effect
Test that can differentiate hyperthyroidism from nonhyperthyroidism
Radioactive iodine uptake
Radioactive iodine uptake is ___ in hyperthyroidism
High
Radioactive iodine uptake is ___ in nonhyperthyroidism
Low
Test that differentiates thyroiditis from exogenous causes of nonhyperthyroidism
Thyroglobulin level
Thyroglobulin level is ___ in thyroiditis
High
Thyroglobulin level is ___ in exogenous causes
Low
Thyroglobulin level is ___ in ectopic causes
High
Hyperthyroidism cause that will present normal TSH level
TSH-secreting tumor
