Lab - Midterms

• Endocrine System

  Composed of glands that secrete hormones into the bloodstream to affect distant organs and regulate body processes
• Hormones

  • Help control mood, growth and development, the way our organs work, metabolism, and reproduction
• Functions of the Endocrine System


  • Metabolism
  • Homeostasis (constant internal balance), such as blood pressure and blood sugar regulation, fluid (water) and electrolyte balance and body temperature
  • Growth and development
  • Sexual function
  • Reproduction
  • Sleep-wake cycle
  • Mood
• Along with the nervous system

  The endocrine system coordinates the body's functions to maintain homeostasis during rest and exercise
• Nervous and endocrine systems

  Work together to initiate and control movement, and all the physiological processes movement involves
• Hormones


  Can affect only a single structure or have multi organ effects
• Chemical compositions of hormones

  Amino acid origin, cholesterol or lipid composition
• Pituitary Gland

  • Anatomically and functionally related to the hypothalamus and attached to it at the tuber cinereum by the infundibulum or pituitary stalk
  • Lies within a bony-walled cavity - sella turcica ("Turkish saddle"), in the sphenoid bone at the base of the brain
  • Consists of Anterior lobe or adenohypophysis and Posterior lobe or neurohypophysis
• 99% of the 1–2 kg of calcium present normally in the adult human body resides in the skeleton
• Calcium in the skeleton


  Provides mechanical stability and serves as a reservoir needed to maintain extracellular fluid (ECF) Ca concentration
• Ionized calcium in ECF must be maintained within a narrow range because of the critical role calcium plays in a wide array of cellular functions
• Cytosolic calcium does not play the structural role instead, it serves a signaling function
• Normal total calcium concentration in blood

  2.2–2.6 mM (8.5–10.5 mg/dL), of which ~50% is ionized
• Remainder of calcium in blood

  Bound ionically to negatively charged proteins (predominantly albumin and immunoglobulins) or loosely complexed with phosphate, citrate, sulfate, or other anions
• PTH


  Increases plasma Ca2+
• Calcitonin


  Decreases plasma Ca2+
• Parathyroid Hormone (PTH)


  1. Direct action: Induces calcium reabsorption in bone and kidneys

  2. Indirect action: Stimulates synthesis of 1,25-dihydroxyvitamin D in kidneys, which stimulates calcium absorption in the GI tract
• 99% of this calcium is in the mineral phase, remaining 1% is freely exchangeable and in equilibrium with ECF
• Plasma Ca


  200mg or 10mg/dL, 41% protein bound, 9% complexed with anions (phosphate), 50% ionized in the biologically active form
• Decrease in serum Ca below 8.8 mg/dL increases secretion of PTH
• Osteoporosis


  • Characterized by decreased bone strength
  • Prevalent among postmenopausal women but also occurs in both women and men as a function of age and with underlying conditions or major risk factors associated with loss of bone mass
  • Chief clinical manifestations: vertebral and hip fractures (also in almost any skeletal site)
• Osteoporosis


  • A reduction in the strength of bone that leads to an increased risk of fractures
  • Loss of bone tissue causes deterioration in skeletal microarchitecture
  • Process of bone loss causes a greater detriment to bone strength than might be appreciated from the simple measure of bone "density"
• Bone mineral density (BMD)


  Measured at lumbar spine, total hip, or femoral neck
• World Health Organization (WHO) definition of osteoporosis


  • Bone density that falls 2.5 standard deviations (SDs) or more below the mean for young healthy adults of same sex and race—also referred to as a T-score of –2.5
  • Postmenopausal women at the lower end of the young normal range (T-score <–1.0) defined as having low bone density and may be at increased risk of osteoporosis
• Thyroid gland


  • Located in the anterior portion of the neck and normally not visible or palpable
  • Releases triiodothyronine (T3) & thyroxine (T4)
  • Controlling metabolism, growth, and many other bodily functions: weight, energy levels, internal temperature, skin, hair, nail growth
• Triiodothyronine (T3) and thyroxine (T4)


  Biologically active thyroid hormones (thyroid gland)
• Thyrotropin-releasing hormone (TRH)


  Stimulates release of thyrotropin (TSH) in response to low circulating levels of thyroid hormone
• Thyroid stimulation hormone (TSH)


  Promotes hormone synthesis and release by increasing thyroid activity
• High circulating thyroid hormone


  Blocks further production by inhibiting TSH release (negative feedback)
• Thyroid disease


  • Hypothyroidism
  • Hyperthyroidism
  • Nodular disease
• Thyrotoxicosis


  State of thyroid hormone excess
• Major etiologies of thyrotoxicosis


  • Graves' disease
  • Toxic multinodular goiter (MNG)
  • Toxic adenomas
• Treatment of hyperthyroidism of Graves' disease


  • Reducing thyroid hormone synthesis with antithyroid drugs
  • Reducing amount of thyroid tissue with radioiodine (131I)
  • Thyroidectomy
• Antithyroid drugs


  Thionamides (Propylthiouracil, Carbimazole, Methimazole) - inhibit the function of TPO, reducing oxidation and organification of iodide, reduce thyroid antibody levels
• Propranolol, atenolol


  Beta blockers used to control adrenergic symptoms in early stages before antithyroid drugs take effect
• Anticoagulation should be considered in all patients with atrial fibrillation by a Cardiologist
• Radioiodine treatment


  • Progressive destruction of thyroid cells used as initial treatment or relapses after a trial of antithyroid drugs
  • Risk of thyrotoxic crisis after radioiodine minimized by pretreatment with antithyroid drugs 1 month before treatment
• Absolute contraindications for radioiodine treatment: Pregnancy and breast-feeding but can conceive safely 6 months after treatment
• Radioiodine treatment generally be avoided in patients with active moderate to severe eye disease
• Thyroidectomy


  • Recommended for patients who relapse after antithyroid drugs and prefer this treatment to radioiodine
  • Some recommend surgery in young individuals, particularly when goiter is very large