HRE TBL 1 - Introduction to the Endocrine System and Hypothalamic-Pituitary Axis

What structure connects the hypothalamus to the pituitary gland?

Infundibulum

Where is the pituitary gland located?

Sella turcica of the sphenoid bone

Which artery supplies the anterior pituitary gland?

Superior hypophyseal artery

Which artery supplies the posterior pituitary gland?

Inferior hypophyseal artery

What is the origin of the anterior pituitary gland?

Rathke's pouch (oral ectoderm)

What is the origin of the posterior pituitary gland?

Neural ectoderm from the diencephalon

Which hormone inhibits prolactin secretion?

Dopamine

What is the most common pituitary adenoma?

Prolactinoma

Which hormone is deficient in central diabetes insipidus?

Antidiuretic hormone (ADH)

What test is used to diagnose diabetes insipidus?

Water deprivation test

What is the function of oxytocin?

Uterine contractions and milk ejection

What hormone stimulates ACTH release?

Corticotropin-releasing hormone (CRH)

What is the function of ACTH?

Stimulates cortisol production from the adrenal cortex

What is the difference between gigantism and acromegaly?

Gigantism occurs before epiphyseal fusion, acromegaly after

What is the diagnostic test for acromegaly?

Glucose suppression test

What is the diagnostic test for adrenal insufficiency?

ACTH stimulation test (Synacthen test)

What is the most common cause of Cushing’s syndrome?

Iatrogenic steroid use

What visual defect is caused by a pituitary macroadenoma?

Bitemporal hemianopia

Which part of the pituitary releases ADH and oxytocin?

Posterior pituitary

What test distinguishes Cushing’s disease from ectopic ACTH?

High-dose dexamethasone suppression test

What hormone stimulates thyroid hormone release?

Thyroid-stimulating hormone (TSH)

What hypothalamic hormone stimulates TSH release?

Thyrotropin-releasing hormone (TRH)

What hormone stimulates FSH and LH release?

Gonadotropin-releasing hormone (GnRH)

What hormone suppresses GH release?

Somatostatin

What hormone stimulates GH release?

Growth hormone-releasing hormone (GHRH)

What is the effect of growth hormone on glucose metabolism?

Anti-insulin effect (increases blood glucose)

What is panhypopituitarism?

Deficiency of all pituitary hormones

What causes Sheehan’s syndrome?

Pituitary infarction due to postpartum hemorrhage

What are symptoms of hypopituitarism?

Fatigue, hypotension, amenorrhea, cold intolerance

What type of feedback regulates most endocrine axes?

Negative feedback

What are the main hormones of the anterior pituitary?

GH, ACTH, TSH, LH, FSH, Prolactin

What are the main hormones of the posterior pituitary?

ADH and Oxytocin

What test evaluates GH and ACTH reserve?

Insulin tolerance test

What is the function of prolactin?

Stimulates milk production

What stimulates prolactin release?

Thyrotropin-releasing hormone (TRH)

What inhibits GnRH in hyperprolactinemia?

Prolactin

What is a craniopharyngioma derived from?

Rathke's pouch remnants

What is the hypothalamic-pituitary-adrenal (HPA) axis sequence?

CRH → ACTH → Cortisol

What is the role of the hypothalamus in endocrine control?

Regulates pituitary hormone release

What are the components of homeostatic control?

Sensor, integrating center, effector

What is the integrating center in most endocrine loops?

Hypothalamus

What is the effector in endocrine homeostasis?

Target endocrine gland

What is the embryological origin of the pituitary stalk?

Neural ectoderm (continuation of diencephalon)

What hormone is elevated in SIADH?

ADH (vasopressin)

What is the treatment for prolactinoma?

Dopamine agonists (e.g., cabergoline)

What is the pathophysiology of central diabetes insipidus?

Deficient ADH secretion from posterior pituitary

What is the pathophysiology of nephrogenic diabetes insipidus?

ADH resistance at the kidney

What is the pathophysiology of acromegaly?

Excess GH after epiphyseal fusion

What hormone is responsible for the stress response?

Cortisol

What does oxytocin do during labor?

Stimulates uterine smooth muscle contractions

Which test confirms acromegaly?

GH suppression after glucose load

What pituitary hormone deficiency can cause infertility?

FSH and LH

What pituitary hormone deficiency causes hypothyroidism?

TSH deficiency

What is the role of TRH besides TSH stimulation?

Stimulates prolactin release

What effect does cortisol have on ACTH and CRH?

Suppresses both via negative feedback

What is the role of the hypophyseal portal system?

Transfers hypothalamic hormones to anterior pituitary

What is the role of the neurohypophyseal tract?

Transfers ADH and oxytocin to posterior pituitary

What is the primary regulator of ADH secretion?

Plasma osmolality

What is the effect of ADH on the kidney?

Increases water reabsorption in the collecting duct

What triggers ACTH release?

Stress and CRH stimulation

What hormone is low in secondary adrenal insufficiency?

ACTH

What is the difference between secondary and primary adrenal insufficiency?

Primary = adrenal problem, Secondary = pituitary problem

What hormone is elevated in Cushing's disease?

ACTH

What hormone is low in Cushing's syndrome from adrenal tumor?

ACTH

What is the feedback mechanism for thyroid hormone?

High T3/T4 suppress TRH and TSH

What hormones regulate the menstrual cycle from the pituitary?

FSH and LH

What happens to ADH levels during dehydration?

They increase

What is the function of LH in males?

Stimulates testosterone production from Leydig cells

What is the function of FSH in males?

Stimulates spermatogenesis via Sertoli cells

What cells secrete GH in the pituitary?

Somatotrophs

What cells secrete prolactin?

Lactotrophs

What cells secrete ACTH?

Corticotrophs

What cells secrete TSH?

Thyrotrophs

What cells secrete FSH and LH?

Gonadotrophs

What is the typical size cut-off between pituitary micro- and macroadenomas?

1 cm

Which pituitary hormone stimulates adrenal androgen production?

ACTH

What is the main imaging modality for pituitary lesions?

MRI with gadolinium contrast

What is the function of the posterior pituitary?

Storage and release of hypothalamic hormones

What is the result of compression of the pituitary stalk?

Hyperprolactinemia

What is the mechanism of dopamine agonists in prolactinoma?

They inhibit prolactin release

What does somatostatin inhibit?

GH and TSH release

What are the symptoms of prolactinoma in men?

Hypogonadism, infertility, galactorrhea (rare)

What structure is directly above the pituitary gland?

Optic chiasm

What structure forms the floor of the third ventricle?

Hypothalamus

What causes visual field defects in pituitary tumors?

Compression of the optic chiasm

What are symptoms of a pituitary macroadenoma?

Headache, vision loss, hormonal deficiency

What is pituitary apoplexy?

Acute hemorrhage or infarction of the pituitary

What are the symptoms of pituitary apoplexy?

Sudden headache, vision loss, hormonal collapse

What test evaluates anterior pituitary reserve?

Insulin tolerance test

What happens to LH and FSH in hypogonadotropic hypogonadism?

They are low

What are the symptoms of diabetes insipidus?

Polyuria, polydipsia, dilute urine

What is the treatment for central diabetes insipidus?

Desmopressin (synthetic ADH)

What is the treatment for nephrogenic diabetes insipidus?

Thiazide diuretics and low-salt diet

What pituitary hormone is under tonic inhibition?

Prolactin

What hypothalamic nuclei produce oxytocin and ADH?

Supraoptic and paraventricular nuclei

What is the primary hypothalamic stimulus for GH secretion?

Hypoglycemia

What is the physiological inhibitor of GH secretion?

Hyperglycemia

What type of receptor detects plasma osmolality?

Osmoreceptor

What type of tissue forms the posterior pituitary?

Neural tissue

Which part of the pituitary is directly innervated by the hypothalamus?

Posterior pituitary (neurohypophysis)