Other Glands

• Hypoparathyroidism causes low calcium levels due to insufficient parathyroid hormone production or resistance.
• The most common cause of hypercalcemia is primary hyperparathyroidism
• Parathyroid hormone (PTH) regulates the balance between calcium and phosphorus in the body.
• Primary hyperparathyroidism can be caused by an adenoma, hyperplasia, or carcinoma of the parathyroid gland.
• Primary hyperparathyroidism is characterized by elevated serum calcium levels with normal or high PTH levels.
• Secondary hyperparathyroidism occurs when there are other conditions that lead to hypocalcemia, such as chronic kidney disease.
• Secondary hyperparathyroidism occurs when there are not enough vitamin D-dependent calcium receptors in the kidneys, leading to increased PTH release.
• Parathyroid gland


  Located on or near the thyroid capsule, sometimes within the thyroid gland, may also be found outside their normal anatomical location in the neck
• Parathyroid gland

  • Most people have 4 parathyroid glands, but some have as few as 2
  • It is the smallest endocrine gland in the body
  • It secretes parathyroid hormone (PTH), a hypercalcemic hormone
• Role of parathyroid hormone

  1. Prevents hypocalcemia (low blood calcium)

  2. Preserves calcium and phosphate within normal range

  3. Promotes bone resorption to release calcium into the bloodstream

  4. Increases renal reabsorption of calcium

  5. Stimulates conversion of inactive Vitamin D to active Vitamin D

  6. Indirectly increases intestinal absorption of calcium
• Clinical disorders of hyperparathyroidism

  • Primary hyperparathyroidism
  • Secondary hyperparathyroidism
  • Tertiary hyperparathyroidism
• Primary hyperparathyroidism


  Most common cause of hypercalcemia, due to the presence of a functioning parathyroid adenoma
• Secondary hyperparathyroidism


  Occurs in response to decreased calcium levels, there is diffuse hyperplasia of all 4 glands
• Tertiary hyperparathyroidism


  Develops in response to long-standing secondary hyperparathyroidism, the patient develops severe bone disease
• Hypoparathyroidism


  Individuals are unable to maintain calcium concentration in blood without calcium supplementation, can be caused by accidental injury to parathyroid glands during surgery or autoimmune parathyroid destruction
• Adrenal gland


  • Has a pyramid-like shape, located above the kidneys, composed of an outer adrenal cortex and inner adrenal medulla
• Zones of the adrenal cortex

  • Zona glomerulosa (10%)
  • Zona fasciculata (75%)
  • Zona reticularis (15%)
• Zona glomerulosa


  Synthesizes mineralocorticoids like aldosterone, responsible for sodium, potassium and acid-base homeostasis
• Zona fasciculata


  Synthesizes glucocorticoids like cortisol, responsible for blood glucose homeostasis
• Zona reticularis


  Synthesizes adrenal androgens like DHEA, precursors for adrenal sex hormones
• Cortisol


  The principal glucocorticoid, its secretion is regulated by ACTH, has anti-inflammatory and immunosuppressive actions
• Aldosterone


  The most potent mineralocorticoid, helps regulate water and electrolyte (sodium, potassium) balance and blood pressure
• Adrenal medulla


  • Composed primarily of chromaffin cells, secretes catecholamines like epinephrine and norepinephrine
• Catecholamines


  The "First Responders" to stress, act within seconds to promote fight-or-flight response
• Catecholamines


  • Dopamine
  • Epinephrine (adrenaline)
  • Norepinephrine (noradrenaline)
• Norepinephrine


  Primary amine, produced by sympathetic ganglia, acts as a neurotransmitter in CNS and sympathetic nervous system
• Epinephrine


  Secondary amine, most abundant medullary hormone, the "fight or flight hormone" released in response to stress
• Dopamine


  Catecholamine produced by decarboxylation of DOPA, present in highest concentrations in the brain
• Testosterone


  The principal androgen hormone in the blood, synthesized by Leydig cells of the testes, controls growth and development of male reproductive system
• Dehydroepiandrosterone (DHEA)


  Weak androgen formed by the adrenal cortex, valuable in assessing adrenal cortex function
• Estrogen


  Carbon-18 steroid hormone that promotes breast development, maturation of external genitalia, and regulation of menstrual cycle
• Forms of estrogen

  • Estrone (E1)
  • Estradiol (E2)
  • Estriol (E3)
• Progesterone


  Produced mainly by the corpus luteum, responsible for the luteal phase of the menstrual cycle, prepares the uterus for pregnancy and breast for lactation