Estrogen

Estrogens (+)

  • Example (R): Raloxifene

  • Estrogens play a vital role throughout a female's reproductive life, particularly in maintaining bone integrity.

    • They inhibit cytokines that recruit osteoclasts, which are cells responsible for bone resorption, and oppose the bone-resorbing, calcium-mobilizing actions of parathyroid hormone (PTH).

  • Mechanism of Action (MoA):

    • Estrogens are effective in preventing accelerated bone loss during the immediate postmenopausal period.

    • They can at least transiently increase bone mass in postmenopausal women, which is crucial for maintaining bone density and preventing osteoporosis.

    • These hormones reduce the bone-resorbing action of PTH, thereby favoring a balance towards bone formation rather than destruction.

    • Administration of estrogens leads to an increase in the levels of 1,25-dihydroxyvitamin D (1.25(OH)2D) in the blood.

      • This rise can be attributed to decreased serum calcium and phosphate levels along with an increase in PTH.

    • Estrogen receptors, which mediate the effects of estrogens, have been identified in bone tissue, indicating that estrogens have direct effects on bone remodeling processes.

  • Pharmacokinetics:

    • Estrogens are well absorbed in the gastrointestinal tract (GIT) and are widely distributed in various tissues.

    • They are converted to active metabolites primarily in the (LLSK) liver, lungs, spleen, and kidneys.

    • The average half-life of estrogens is approximately 32 hours, allowing for sustained action in the body.

    • Excretion occurs primarily via feces.

  • Uses (HP):

    • Hormone replacement therapy (HRT) for alleviating menopausal symptoms.

    • Prevention and treatment of postmenopausal osteoporosis, an important consideration given the increased risk of fractures in this population.

  • Side Effects (HLV):

    • Common side effects include hot flashes and leg cramps, which some patients may experience with hormone therapy.

    • There is a potential risk of venous thromboembolism, which necessitates careful patient selection and monitoring during treatment.