Physiology - Block 1 - Part 3

davidwurbel7's version from 2015-06-07 03:56

Anterior Pituitary

Question Answer
Somatotrophs and LactotrophsAcidophils
Gonadotrophs, Thyrotrophs, and CorticotrophsBasophils
Cells without any granulesChromophobes
Most common tumor of the pituitary. Arises from acidophils which produces prolactinProlactinoma
Second common tumor of the pituitary. Arises from acidophils which produce GHSomatonoma
Third common tumor of the pituitary. Arises from basophils with produce ACTHCorticonoma
A non-producing tumor of that is usually >1 cm in size which arises from the chromophobesMacroadenoma
Hyper pigmentation is seen in Addison’s Disease which over production of which pituitary hormoneACTH
A single chain polypeptide hormone; Has Species specificity; Structural resemblance to PRL (Prolactin) & Human Placental Lactogen (HPL); Released in a pulsatile manner; Mechanism of action - Acts via cell membrane receptorsGrowth Hormone (GH)
Decreased glucose concentrationStimulatory Factors
Decreased free fatty acid concentrationStimulatory Factors
ArginineStimulatory Factors
Fasting or starvationStimulatory Factors
Hormones of puberty (estrogen, testosterone)Stimulatory Factors
ExerciseStimulatory Factors
StressStimulatory Factors
Stage III and IV sleepStimulatory Factors
α-Adrenergic agonistsStimulatory Factors
Increased glucose concentrationInhibitory Factors
Increased free fatty acid concentrationInhibitory Factors
ObesityInhibitory Factors
SenescenceInhibitory Factors
SomatostatinInhibitory Factors
SomatomedinsInhibitory Factors
Growth hormoneInhibitory Factors
β-Adrenergic agonistsInhibitory Factors
PregnancyInhibitory Factors
Secretion of GH requires presence of normal levels of this hormoneThyroid Hormone
Circulate in blood binding to protein (half life is very long 20hrs), blood level serves as a reflection of 24-hr growth hormone secretion as GH is secreted in pulsesIGF-1
Opposes the action of insulinGH
Near the end of puberty, these hormones promote the mineralization (fusion or closure) of the epiphyseal plates of long bonesAndrogens
Hormones that raise blood glucose levels include GH, Cortisol, Glucagon and EpinephineCounter-Regulatory Hormones
Condition due to panhypopituitarism is lack of all Anterior Pituitary hormones, Decreased GHRH / IGF-1, Hypophysectomy (Removal of Pituitary gland), HypothyroidismDwarfism
In this condition, plasma GH levels are elevated, but GH receptors are defectiveLaron Dwarfism / GH insensitivity
Caused by ↓ GH ,↓GHRH; Plumpiness, Immature face,Small genitalia; Body proportion according to chronological age; Delayed skeletal & dental; development; ↓circulating levels of GHPituitary Dwarfism
Caused by ↓Thyroid hormone; Gross retardation of mental & physical development; Infantile body proportion; Other features of hypothyroidismHypothyroid Dwarfism (Cretin)
Is seen due to overproduction of GH during adolescence, before puberty (before epiphyseal closure) resulting in excessive growth of long bonesGigantism (Giantism)
Clinical features include tall stature (up to 8 ft / 2.5 m). Large hands & feet. Other associated features include bilateral gynaecomastia (enlargement of breasts due to structural similarity of GH to Prolactin). Coarse facial features due to increased tissue proliferationGigantism (Giantism)
Occurs due to excessive secretion of GH during adulthood (after epiphyseal closure)Acromegaly
Clinical features include prognathism (elongation & widening of mandible) Prominent brow, Bulbous nose. There is thickening of skin & coarse facial features. Proliferation of connective tissue resulting in Facial edema. Increased Blood glucose levels ( as GH is diabetogenic). Kyphosis - periosteal growth of vertebrae. Enlarged hands & feet (Acral parts) - periosteal growth of metatarsals & metacarpals Hypertrophy of soft tissues - Heart (Cardiomegaly) - Liver (Hepatomegaly) - Kidney (Renomegaly) - Spleen (Splenomegaly) - Tongue & musclesAcromegaly
Due to pressure on the optic chiasm the loss of peripheral vision in both eyesBilateral Hemianopia
Treatment for both Giantism and AcromeglySomatostatin Analogues
Anterior Pituitary which is highly vascular, gets enlarged during pregnancy. During childbirth, if mother suffers post partum hemorrhage, leading to pituitary infarction and necrosis (mostly likely gonadotrophs) giving rise to decreased levels of all the anterior pituitary hormones resulting in panhypopituitarismSheehan’s Syndrome
With total pituitary necrosis, all hormones of this part of the pituitary decreaseAnterior Pituitary
With total pituitary necrosis, all hormones of this part of the pituitary initially decrease but then return to normal levelsPosterior Pituitary
A single chain polypeptide. Receptors resemble GH receptors. Structurally similar to GHProlactin (PRL)
Increases during pregnancy & lactationProlactin (PRL)
A major hormone responsible for Lactogenesis. Stimulates milk production in the breasts by formation of Casein & Lactalbumin. Stimulates breast development along with EstrogenProlactin (PRL)
Inhibits Ovulation by decreasing synthesis & release of Gonadotropin Releasing Hormone (GnRH) from Hypothalamus (Females). Inhibits spermatogenesis by decreasing GnRH (Males)Prolactin (PRL)
The receptor on lactotrophs that binds dopamineD2 Receptor
In high levels, TSH can stimulate the production of prolactin in which conditionHypothyroidism
Estrogen (during Pregnancy stimulates lactotropes), Breast feeding, TRH, Dopamine antagonistsIncrease Prolactin Secretion
Dopamine, Bromocryptine (Dopamine agonist), Somatostatin, PRL (by negative feedback)Decrease Prolactin Secretion
Inhibits mRNA production & inhibits synthesis of milk proteins. Therefore this hormone increases PRL secretion but INHIBITS actions of PRLEstrogen
PRL excess resulting from Hypothalamic lesions – due to loss of inhibitory control of PIF (Dopamine) on PRL secretion. Prolactinomas – PRL secreting tumors of Anterior PituitaryHyperprolactinemia
Clinical Features: Galactorrhea. Amenorrhea (Lack of Menstrual cycles) is seen because PRL inhibits GnRH release from Hypothalamus causing decreased FSH & LH & failure to ovulate. In females – Infertility & Amenorrhea. In males – Gynaecomastia & ImpotenceHyperprolactinemia
Dopamine agonists like Bromocryptine/Cabergoline which decreases PRL secretionHyperprolactemia
An autosomal dominant familial tumor syndrome (also termed Wermer syndrome). People develop tumors of the parathyroid glands, the enteropancreatic neuroendocrine system, the anterior pituitary gland, and the skin. The most common endocrine tumors are parathyroid tumors that cause hyperparathyroidism and hypercalcemiaMultiple Endocrine Neoplasia Type 1 (MEN1)

Posterior Pituitary

Question Answer
ADH is also called ___________ because of its vasoconstrictor action via V1 receptors (IP3 and DAG)Vasopressin
Binds to V2 receptors stimulating Adenylyl cyclase activity (cAMP) in renal tubules.ADH
Major factors regulating secretion of this hormone are changes in plasma Osmolarity (Osmotic stimuli) and Volume changesADH
These factor increase the secretion of this hormone increase in plasma/ECF osmolarity. Decrease in plasma/ECF volume, Angiotensin II, Pain/stressADH
These factor decrease the secretion of this hormone decrease in plasma/ECF osmolarity. Increase in plasma/ECF volume, ANP, Alcohol, WeightlessnessADH
ADH is synthesized predominantly in this part of hypothalamus and stored in posterior pituitarySupraoptic Nucleus
These are stimulated by increase in osmolarity of ECF/plasmaOsmoreceptors
These activate ADH neurons in the hypothalamus and stimulate consumption of water through hypothalamic centers regulate thirstOsmoreceptors
Secretion of this hormone is most sensitive to plasma osmolarity but will also be secreted if blood volume decreases or cardiac output fails even at the cost of a drop in blood osmolarityADH
A syndrome that results when there is Vasopressin deficiency or when kidneys fail to respond to ADHDiabetes Insipidus
A syndrome that results when there is damage to the hypothalamus resulting in low or no ADH to be productiveNeurogenic Diabetes Insipidus
A syndrome that results when there is defect to ADH receptors causing ADH insensitivity or defect in aquaporinsNephrogenic Diabetes Insipidus
To differentiate between the 2 forms, give exogenous ADH - If there is a response (Urine Osmolarity increases)Neurogenic Diabetes Insipidus
To differentiate between the 2 forms, give exogenous ADH - If there is no response (Urine osmolarity fails to increase)Nephrogenic Diabetes Insipidus
What test is use to differiate from Primary Polydipsia and Diabetes InsipidusWater Depravation Test
↑ Plasma ADH, ↑ Plasma Osmolarity, ↑ Urine Osmolarity, ↓ Urine Volume, Negative free water clearanceWater Deprivation
↓ Plasma ADH, ↓ Plasma Osmolarity, ↓ Urine Osmolarity, ↑ Urine Volume, Positive free water clearancePrimary Polydipsia
↓↓ Plasma ADH, ↑ Plasma Osmolarity, ↓ Urine Osmolarity, ↑ Urine Volume, Positive free water clearanceNeurogenic Diabetes Insipidus
↑ Plasma ADH, ↑ Plasma Osmolarity, ↓ Urine Osmolarity, ↑ Urine Volume, Positive free water clearanceNephrogenic Diabetes Insipidus
↑↑ Plasma ADH, ↓ Plasma Osmolarity, ↑ Urine Osmolarity, ↓ Urine Volume, Negative free water clearanceSyndrome of Inappropriate ADH (SIADH)
Originates in Paraventricular nucleus (PVN) of Hypothalamus and transported by its carrier protein Neurophysin IOxytocin
Factors increasing the release include suckling, sight / smell / sound of baby’s cry, dilatation of cervix (Parturition), orgasmOxytocin
Factors decreasing the release include stress, fright and drugs - Opiods, AlcoholOxytocin
A slow-growing, extra-axial, epithelial-squamous, calcified cystic tumor arising from remnants of the craniopharyngeal duct and/or Rathke cleftCraniopharyngioma
The most common presenting symptoms are headache , endocrine dysfunction and visual disturbances (loss of peripheral vision). Headache is slowly progressive, dull, continuous and it becomes severe in most patients when endocrine symptoms become obviousCraniopharyngioma