Endocrine - Pituitary Flashcards
Endocrine Glands
Secrete hormones DIRECTLY into surrounding extracellular fluid
Exocrine Glands
Products are discharged via ducts
What mediates the endocrine system?
HORMONES
What are hormones?
Chemical messengers that transport information from initial cells to target cells
Hormone Secretion Regulation
- Neural control
- Biorhythms
- Feedback mechanisms
Hormone Neural Control
Suppress or stimulate hormone secretion
Stimuli include pain, smell, touch, stress, sight, taste
Catecholamines, ADH, & cortisol are hormones under neural control
Hormone Biorhythms
Genetically encoded or acquired biorhythms
Intrinsic hormonal oscillations - circadian, weekly, or seasonal
Potential to vary w/ life stages
Hormone Feedback Mechanisms
Negative or positive
Anterior Pituitary
Adenohypophysis 80% pituitary Secretes 6 hormones - Growth hormone - Adrenocorticotropic ACTH - Thyroid-stimulating TSH - Follicle-stimulating FSH - Luteinizing hormone - Prolactin
TSH
Thyrotropin-releasing hormone TRH → TSH
Target site = thyroid glands
ACTH
Corticotropin-releasing hormone CRH → ACTH
Target site = adrenal cortex zona fasiculata & reticularis
CORTISOL
FSH/LH
Gonadotropin-releasing hormone → FSH/LH
Target site = gonads (testes/ovaries)
Estrogen, progesterone, testosterone
Prolactin
Anterior pituitary hormone
Prolactin releasing & inhibitory hormone/factor
Lactotroph
Target site = breasts
Growth Hormone
Anterior pituitary hormone
Growth hormone releasing & inhibitory hormone/factor
Somatotroph
Target site = all tissues
Primary Pituitary Disorder
Defect to the peripheral endocrine gland (target organ)
Secondary Pituitary Disorder
Pituitary defect (ex: tumor)
Tertiary Pituitary Disorder
Hypothalamus defect (not common)
Panhypopituitarism
Generalized pituitary hypofunction
Panhypopituitarism Causes
Non-functioning tumors compress & destroy normal pituitary tissue Hypophysectomy Postpartum shock Irradiation Trauma Infiltrative disorders
Anterior Pituitary Hyposecretion
Treatment
Surgical tumor removal
Hormone replacement therapy - thyroid hormone, glucocorticoids, vasopressin
Anterior Pituitary Hypersecretion
Usually caused by benign adenomas
Prolactin → amenorrhea, infertility, ↓libido, impotence
ACTH → Cushing’s disease
Growth hormone → promotes growth all tissues capable to grow
Tumors that secrete thyrotropin or gonadotropin are rare
Growth Hormone Normal Secretion
Secretion increases during stress, hypoglycemia, exercise, & deep sleep
Stimulate insulin-like growth factor type 1 (IGF-1) production that mediates GH effects
Skeletal muscle, heart, skin, & visceral organ undergo hypertrophy & hyperplasia d/t GH & IGF-1
Growth Hormone Hypersecretion
Usually caused by GH secreting pituitary adenoma
Gigantism
GH hypersecretion prior to puberty or before growth plates closure
8-9’ tall
Acromegaly
GH hypersecretion in adults after growth plates closed (adolescence)
Sustained GH hypersecretion → tissue growth
Acromegaly S/S
Skeletal & soft tissue overgrowth Large mandible & tongue → potential difficult intubation Tissue hypertrophy around vocal cords Visceromegaly Osteoarthritis Glucose intolerance Skeletal muscle weakness Extrasellar tumor excision
Acromegaly Comorbidities
HTN, cardiomyopathy, & ischemic heart disease
Diabetes
Osteoarthritis & skeletal muscle weakness/fatigue
↑lung volumes & sleep apnea
Organ enlargement - liver, spleen, kidneys, heart
Acromegaly Treatment
Restore normal GH levels
Preferred initial treatment - microsurgical tumor removal w/ gland preservation
Small tumors transsphenoid approach
Large tumors intracranial approach
Irradiation and/or suppressant drug therapy as adjunct to shrink tumor for non-surgical candidates
Acromegaly Anesthetic Considerations
Difficult mask/airway
Sleep apnea
Postop respiratory obstruction or failure
Systemic HTN, ischemic heart disease, arrhythmias
Monitor blood glucose
Stress-level glucocorticoid therapy & thyroid replacement
Pituitary Surgery
Preop Evaluation
Check electrolytes, hormone levels, & glucose
Imaging to assess tumor extent
EKG to assess LV hypertrophy or arrhythmias
Consider echo w/ cardiac dysfunction patients
Optimize cardiac function prior to surgery
Check collateral wrist circulation prior to A-line insertion (potential ulnar flow impede d/t carpal tunnel ligament hypertrophy)
Transsphenoid Approach
Elevate HOB 15° A-line Lumbar drain VAE risk Submucosal epi injections to vasoconstrict → HTN Intraop hypotension d/t inadequate cortisol secretion Muscle relaxation & smooth extubation Neurological exam postop
Transsphenoid Approach Complications
Cranial nerve damage Epistaxis Hyponatremia CSF leak Diabetes insipidus
Posterior Pituitary
Neurohypophysis
20% pituitary
Secretes ADH (vasopressin) & oxytocin (Pitocin)
ADH
Antidiuretic hormone or vasopressin
Controls renal water reabsorption
Regulates serum osmolarity
Oxytocin
Stimulates uterine contractions
Breast myoepithelia cells - milk ejection during lactation
Induces labor & decreases postpartum bleeding
Vasopressin Receptors
V1 - mediates vasopressin (refractory hypotension)
V2 - mediates water reabsorption in renal collecting ducts (DDAVP target site)
V3 - located in CNS & stimulates corticotrophin secretion modulation
Stimuli to release ADH:
↑plasma Na+ ↑serum osmolality ↓blood volume Smoking (nicotine) Pain or stress Nausea Vasovagal reaction ANG II PPV
Diabetes Insipidus
Cause: surgical trauma to posterior pituitary
Reversible
Insufficient ADH
↑UOP ↓urine osmolarity & specific gravity ↑serum electrolytes
Hypernatremia
DI Types
Neurogenic or central caused by inadequate ADH release
Nephrogenic - renal tubular resistance to ADH
Neurogenic DI Causes
Head trauma
Brain tumors
Neurosurgery
Infiltrating pituitary lesions
Nephrogenic DI
Associated w/
- Hypo/hyperkalemia
- Genetic mutations
- Hypercalcemia
- Medication induced nephrotoxicity
ADH Deficiency S/S
Polyuria >2mL/kg/hr
Dilute unconcentrated urine
Dehydration
Hypernatremia Na+ >145mEq/L
↑serum plasma osmolarity >290mOsm/L
↓urine osmolarity <300mOsm/L & specific gravity <1.01
Neurological hyperreflexia, weakness, lethargy, seizures, & coma
Significant/Complete DI
Plasma osmolarity >290mOsm/L
DI Treatment
Monitor UOP & electrolytes DDAVP or vasopressin Restrict Na+ intact Adequate fluid replacement UO 1:1
DDAVP
Desmopressin ↑factor VIII Selective V2 agonist Admin 30-90min before surgery DOA 8-12 hours Less V1 (vasopressor) activity Enhanced antidiuretic properties Nasal 5-40mcg/day SQ 0.5-2mcg/day BID
Posterior Pituitary Preop Assess
Assess plasma electrolytes, renal function, & plasma osmolarity
Dehydration → sensitive to general anesthesia hypotensive effects
Replace intravascular volume w/ isotonic fluids over 24-48hrs
ADH Deficiency Preop Treatment
Surgery stress increases ADH secretion
Complete DI pre-treat w/ DDAVP 1-2mcg IV Q12H
Vasopressin 5-10 units IM/SQ Q8-12H
Caution w/ CAD patients → HTN d/t arterial vasoconstriction
Measure UOP, plasma osmolarity, & serum Na+
Admin isotonic fluids
SIADH
Syndrome inappropriate antidiuretic hormone
↑ADH ↑renal H2O reabsorption despite hyponatremia & plasma hypotonicity
Intracellular & extracellular fluid expansion
Hemodilution & weight gain
UOP hypertonic/concentrated related to plasma
SIADH Causes
Hypothyroidism Pulmonary infection Small cell lung carcinoma Head trauma Intracranial tumors Pituitary surgery Medications
SIADH S/S
Water intoxication ↓serum osmolarity <270mOsm/L Dilutional hyponatremia <130mOsm/L ↓UOP Hypertonic/concentrated urine Neurological cerebral edema → lethargy, headache, nausea, confusion, seizures, & coma
SIADH Treatment
Mild - fluid restriction 800-1,000mL/day NS
Consider hypertonic saline (symptomatic patients or serum Na+ <115-120mEq/L) w/ or w/o loop diuretic
Monitor serum Na+ Q2H
Sodium Replacement
SLOWLY
1-2mEq/L/hr or 6-12mEq/L/day
Prevent acute loss brain H2O
Central pontine demyelination syndrome → permanent neurological damage
SIADH Anesthetic Considerations
Isotonic solution w/ fluid restriction
CVP to help monitor fluid status & guide replacement therapy
Closely monitor UOP, urine osmolarity, plasma osmolarity, & serum Na+ concentration
Prevent nausea → triggers ADH release
