Updated: 6/23/2018

Pituitary (Hypophysis)

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https://upload.medbullets.com/topic/109002/images/pituitary_gland.jpg
Overview
 
  • Overview 
    • pituitary, or hypophysis, rests in sella turcica, a depression of the sphenoid bone
    • primary function of pituitary is secretion of hormones
    • anatomically, pituitary is divided into anterior and posterior pituitary
Anterior Pituitary: Anatomy and Embryology
  • Anterior pituitary 
    • anterior pituitary, or adenohypophysis, is the glandular component of the pituitary
      • a collection of endocrine cells
        • responsible for synthesis and secretion of anterior pituitary hormones
    • consists of pars distalis, pars intermedia,and  pars tuberalis
    • embryological origin
      • oral ectoderm (Rathke's pouch)
        • upgrowth of oral ectoderm
        • primitive oral cavity
  • Anterior pituitary cell types
    • various cell types are responsible for synthesis and secretion of various hormones
    • gonadotrophs
      • FSH and LH
    • corticotrophs
      • ACTH
    • thyrotrophs
      • TSH
    • lactotrophs
      • prolactin
    • somatotrophs
      • growth hormone (somatotropin)
  • Histology
    • chromophils
      • anterior pituitary cells that contain granules that react with acidophilic/basophilic stains
        • acidophils
          • anterior pituitary cells (pars distalis) that contain granules that react with acidophilic stains
          • responsible for synthesis and secretion of PiG hormones
            • prolactin and growth hormone
        • basophils 
          • anterior pituitary cells (pars distalis) that contain granules that react with basophilic stains
          • responsible for synthesis and secretion of FLAT hormones
            • FSH, LH, ACTH, TSH
              • granules that contain FLAT hormones are PAS+
    • chromophobes
      • anterior pituitary cells that lack granules and that do not react with acidophilic/basophilic stains
        • e.g., stromal cells and degranulated chromophils
Anterior Pituitary: Hormones
  • Anterior pituitary hormones
    • FLAT PiG
      • FSH (follicle-stimulating hormone)
      • LH (luteinizing hormone)
      • ACTH (adrenocorticotropic hormone)
      • TSH (thyroid-stimulating hormone)
      • Prolactin
      • Growth hormone (somatotropin)
    • categories of hormones
      • corticolipotropins
        • ACTH and MSH (melanocyte-stimulating hormone)
      • glycoprotein hormones
        • FSH, LH, TSH
      • somatomammotropins
        • prolactin and growth hormone
  • Cortiolipotropins
    • synthesis
      • overview
        • corticolipotropins are derived from a single precursor, POMC
          • POMC = pro-opiomelanocortin
      • pathway details
      • MSH
        • corticolipotropin synthesis products (aka fragments) contain MSH
        • increased MSH levels skin pigmentation
        • e.g., Addison's disease
          • ↑ ACTH ↑ MSH skin pigmentation
  • Glycoprotein hormones
    • subunits of peptide hormones
      • glycoprotein hormones contain 2 subunits: α and β subunit
        • α subunits identical, β subunits non-identical
          • hormone specificity determined by β subunit
      • human chorionic gonadotropin (hCG) structurally related to glycoprotein hormone
        • hCG contains identical α subunit
  • Somatomammotropins
    • prolactin
    • growth hormone
      • secretion
        • pulsatile secretory pattern
          • secretory bursts approximately every 2 hours
            • ↑ in secretory bursts during exercise and sleep
      • functions
        • ↑ linear growth and muscle mass
          • growth mediated by production of somatomedins
            • aka insulin-like growth factors (IGFs)
        • diabetogenic effect
          • insulin resistance
            • decreases glucose uptake and utilization
          • "diabetogenic"
            • growth hormone produces increases in blood glucose
      • pathophysiology
        • GH deficiency
          • before puberty
            • symptoms
              • failure to grow
              • short stature
              • mild obesity
              • delayed puberty
          • treatment
            • growth hormone replacement
        • GH excess
          • growth-hormone secreting pituitary adenoma causes acromegaly
          • symptoms differ from pre-puberty vs post-puberty
            • before puberty
              • gigantism
                • aka increased linear growth
            • after puberty
              • increased organ size
              • increased hand and foot size
              • enlargement of tongue
              • coarsening of facial features
              • insulin resistance and glucose intolerance
          • treatment
            • somatostatin analog (e.g., octreotide)
Posterior Pituitary: Anatomy and Embryology
  • posterior pituitary
    • posterior pituitary, or neurohypophysis, is the neural portion of the pituitary
      • a collection of unmyelinated axons
        • axons extend from cell bodies in hypothalamus
    • consists of pars nervosa, infundibular stalk, and median eminence
    • neurophysins carry hormones made in the hypothalamus (ADH and oxytocin) from the hypothalamus to the posterior pituitary
    • embryological origin
      • neural ectoderm
        • downgrowth of neural ectoderm (diencephalon)
Posterior Pituitary: Hormones
  • Antidiuretic hormone (ADH; vasopressin) 
    • synthesis
      • hypothalamic supraoptic nucleus neuronal cell bodies synthesize ADH pro-hormone
        • ADH pro-hormone contains ADH and neurophysin II
      • ADH pro-hormones are packaged in secretory vesicles
        • secretory vesicles are transported via axonal transport to nerve terminals
          • nerve terminals in pars nervosa of posterior pituitary
      • ADH pro-hormone processing occurs in secretory vesicles during axonal transport
        • cleavage of neurophysin II and release of ADH hormone
    • secretion
      • action potential depolarizes nerve terminals
        • neurosecretory vesicles fuse with plasma membrane
          • releases ADH and neurophysin II into perivascular space of highly fenestrated capillaries by which ADH enters systemic circulation
  • Oxytocin
    • synthesis
      • neuronal cell bodies of the hypothalamic paraventricular nucleus synthesize oxytocin pro-hormone
        • oxytocin pro-hormone contains oxytocin and neurophysin I
      • oxytocin pro-hormones are packaged in secretory vesicles
        • secretory vesicles are transported via axonal transport to nerve terminals
          • nerve terminals in pars nervosa of posterior pituitary
      • oxytocin pro-hormone processing occurs in secretory vesicles during axonal transport
        • cleavage of neurophysin I and release of oxytocin hormone
    • secretion
      • action potential depolarizes nerve terminals
        • neurosecretory vesicles fuse with plasma membrane
          • releases oxytocin and neurophysin I into perivascular space of highly fenestrated capillaries by which oxytocin enters systemic circulation
 

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Questions (2)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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