Leuprolide (Lupron)

Prescription

Leuprolide acetate (brand names Lupron, Eligard, Fensolvi) is a synthetic nonapeptide analog of gonadotropin-releasing hormone (GnRH, also known as LHRH) with a single amino acid substitution (D-Leu at position 6 and ethylamide at the C-terminus) that dramatically increases receptor affinity and resistance to enzymatic degradation compared to native GnRH. Developed by Abbott Laboratories (now AbbVie) and first approved by the FDA in 1985, leuprolide has become one of the most widely prescribed peptide therapeutics worldwide, with over three decades of clinical data supporting its efficacy and safety across multiple indications. The pharmacology of leuprolide exploits the biphasic response of the pituitary-gonadal axis to continuous GnRH receptor stimulation. Native GnRH is secreted in a pulsatile pattern (approximately every 60–90 minutes) that is essential for maintaining normal LH and FSH secretion. When a potent GnRH agonist like leuprolide is administered as a depot formulation providing continuous receptor stimulation, an initial stimulatory phase (the flare response) occurs during the first 1–2 weeks, transiently increasing LH, FSH, and sex steroid levels. This is followed by receptor downregulation and desensitization, leading to profound suppression of the entire hypothalamic-pituitary-gonadal axis — effectively creating a reversible medical castration with testosterone or estrogen levels falling to castrate range. Clinically, leuprolide is FDA-approved for advanced prostate cancer (where testosterone suppression is the primary goal), endometriosis (where estrogen suppression reduces ectopic endometrial tissue growth), uterine fibroids (preoperative shrinkage), and central precocious puberty (where it suppresses premature pubertal development). Depot formulations are available in 1-month, 3-month, 4-month, and 6-month intramuscular or subcutaneous injection intervals, making compliance straightforward. The 6-month depot (Lupron Depot 45 mg) represents one of the longest-acting peptide formulations in clinical use. Side effects are predictable consequences of sex steroid suppression: hot flashes, decreased libido, erectile dysfunction in men, bone density loss with prolonged use, mood changes, and fatigue. These effects are reversible upon treatment discontinuation, with hormonal recovery typically occurring within 3–6 months. Add-back therapy with low-dose norethindrone or other hormonal agents is standard practice in endometriosis treatment to mitigate hypoestrogenic side effects while maintaining therapeutic efficacy.