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Endocrine Glands: Thyroid, Parathyroid, and Adrenal Glands

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Terms in this set (21)

  • Location and structure of the thyroid gland
    The thyroid gland is located in the anterior neck with right and left lobes connected by the isthmus. It is composed microscopically of thyroid follicles and parafollicular cells.
  • Hormones secreted by the thyroid gland
    The thyroid gland secretes thyroid hormones (T3 and T4) that regulate growth and metabolism, and calcitonin which helps regulate calcium ion homeostasis.
  • Difference between T3 and T4 thyroid hormones
    T3 (triiodothyronine) contains 3 iodine atoms and is more physiologically active, while T4 (thyroxine) contains 4 iodine atoms and is converted into T3 in target cells.
  • Effects of thyroid hormones on metabolism
    Thyroid hormones increase basal metabolic rate by stimulating ATP synthesis, gluconeogenesis, and thermoregulation to maintain core body temperature.
  • Role of thyroid hormones in growth and development
    Thyroid hormones are essential for normal bone growth, muscle growth, and nervous system development.
  • Synergism of thyroid hormones with the sympathetic nervous system
    Thyroid hormones upregulate receptors for sympathetic neurotransmitters, helping regulate blood pressure, heart rate, and other sympathetic actions.
  • Steps in thyroid hormone production
    Iodide ions are absorbed and secreted into colloid, converted to iodine, attached to thyroglobulin forming MIT and DIT, then T3 and T4 are cleaved and released into blood.
  • Negative feedback regulation of thyroid hormone production
    Hypothalamus secretes TRH, stimulating anterior pituitary to release TSH, which promotes T3 and T4 production; high T3/T4 levels inhibit TRH and TSH secretion.
  • Causes and symptoms of Graves disease
    An autoimmune hyperthyroidism where abnormal proteins mimic TSH, causing weight loss, heat intolerance, heart rhythm disruptions, and goiter with bulging eyes.
  • Causes and symptoms of hypothyroidism
    Caused by iodine deficiency or autoimmune destruction (Hashimoto thyroiditis), leading to weight gain, cold intolerance, slow heart rate, and goiter.
  • Function of calcitonin
    Calcitonin, produced by parafollicular cells, lowers blood calcium by inhibiting osteoclast activity, especially during high blood calcium levels.
  • Role of parathyroid hormone (PTH)
    PTH increases blood calcium by stimulating osteoclasts, enhancing intestinal calcium absorption via vitamin D activation, and increasing kidney calcium reabsorption.
  • Regulation of blood calcium by PTH
    Low blood calcium stimulates parathyroid chief cells to secrete PTH, which raises calcium levels; when normalized, PTH secretion decreases.
  • Anatomy of the adrenal gland
    The adrenal gland sits atop the kidneys, with an outer cortex (zona glomerulosa, fasciculata, reticularis) producing steroid hormones, and an inner medulla producing catecholamines.
  • Hormones produced by adrenal cortex zones
    Zona glomerulosa produces mineralocorticoids (aldosterone), zona fasciculata produces glucocorticoids (cortisol), and zona reticularis produces androgens.
  • Effects of aldosterone
    Aldosterone regulates sodium and potassium levels, maintains blood pressure by promoting water reabsorption, regulates acid-base balance, and controls extracellular fluid volume.
  • Regulation of aldosterone secretion
    Stimulated by high potassium, low blood pH, and angiotensin II; ACTH from anterior pituitary also stimulates aldosterone production.
  • Disorders of aldosterone secretion
    Hyperaldosteronism causes hypokalemia, hypernatremia, and hypertension; often due to tumors or idiopathic causes.
  • Effects and regulation of cortisol
    Cortisol promotes gluconeogenesis, releases amino and fatty acids, acts as an anti-inflammatory, and is regulated by the HPA axis via CRH and ACTH.
  • Disorders of cortisol secretion
    Hypercortisolism causes Cushing's disease with fat redistribution and immune suppression; adrenal insufficiency (Addison disease) causes hormone deficiency and electrolyte imbalance.
  • Function of adrenal medulla
    Chromaffin cells secrete epinephrine and norepinephrine in response to sympathetic stimulation, mediating fight-or-flight responses like increased heart rate and bronchiole dilation.