Is goserelin FDA-approved, and what does the research show?

What is goserelin?

Goserelin is a synthetic version of GnRH, gonadotropin-releasing hormone, the signal the brain sends to the pituitary gland to control the testes and ovaries ¹. The label calls it a "synthetic decapeptide analogue of GnRH," a chain of ten amino acids with changes at two positions of the natural hormone's chain ¹. It is a GnRH agonist: a drug that switches the GnRH receptor on rather than blocking it ¹. Given continuously, it makes the pituitary stop responding ¹.

Zoladex is not a liquid injection but an implant, a cylinder about a millimeter across ¹. The drug is dispersed in a polymer of lactic and glycolic acids that the body breaks down ¹. The implant comes preloaded in a syringe and is placed under the skin of the lower abdominal wall, where it releases the drug continuously as it dissolves ¹, ². It comes in two strengths, one released over about a month and one over about three months ¹, ².

Is goserelin FDA-approved?

Yes. Goserelin is an FDA-approved prescription medicine, sold as the Zoladex implant ¹, ². Drugs@FDA, FDA's register of approved drug applications, listed three Zoladex applications on November 6, 2026 ³. The first, NDA 019726 for the 3.6 mg implant, was approved on December 29, 1989 as a new molecular entity, a drug FDA had never approved before ⁴. A second application for the same implant, which FDA's record classes as a new indication without naming it, followed on December 18, 1995 ⁵.

The 10.8 mg implant, NDA 020578, followed on January 11, 1996 as a new dosage form ⁶. All three carry the marketing status "Prescription," and no other company holds a goserelin application ³. The approved uses are specific, and every one of them turns on the sex hormones ¹, ².

FDA approves it, in the 3.6 mg label's words, "in combination with flutamide for the management of locally confined Stage T2b-T4 (Stage B2-C) carcinoma of the prostate" ¹. That treatment starts before radiation therapy and continues during it, with flutamide, another prostate cancer drug the label pairs with it ¹. The label also indicates it "in the palliative treatment of advanced carcinoma of the prostate" ¹. Palliative means treatment that controls the disease and its symptoms rather than cures it.

For women, the label indicates it "for the management of endometriosis, including pain relief and reduction of endometriotic lesions for the duration of therapy" ¹. Endometriosis is a condition in which tissue like the womb's lining grows outside the womb. The label says experience "has been limited to women 18 years of age and older treated for 6 months" ¹. It indicates it "as an endometrial-thinning agent prior to endometrial ablation for dysfunctional uterine bleeding" ¹. Ablation is surgery that destroys the womb's lining to reduce heavy bleeding.

The label also indicates it "in the palliative treatment of advanced breast cancer in pre- and perimenopausal women" ¹. It adds that tests of the tumor for estrogen and progesterone receptors, the proteins those hormones act through, "may help to predict whether ZOLADEX therapy is likely to be beneficial" ¹. The 10.8 mg label indicates the two prostate cancer uses only ².

Neither label indicates it for weight, muscle, longevity, wellness or athletic performance ¹, ². Goserelin is not a wellness, weight or performance peptide; its approved job is to switch the sex hormones off in cancers and conditions those hormones drive ¹, ². Both labels say the implant is placed "under the supervision of a physician," and the route to it is a licensed clinician's prescription ¹, ².

See the FDA status of every peptide, updated weekly.

How does goserelin work?

The first implant stimulates before it suppresses, and the suppression is the treatment ¹. In men, the label says the first implant "causes an initial increase in serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels with subsequent increases in serum levels of testosterone" ¹. LH and FSH are the pituitary's two messengers to the testes and ovaries ¹. That first rise is the flare, and in a cancer fed by the hormone it can briefly worsen symptoms ¹.

Then, with continued exposure, the pituitary stops responding ¹. The label says "chronic administration of ZOLADEX leads to sustained suppression of pituitary gonadotropins" ¹. Testosterone then falls "into the range normally seen in surgically castrated men approximately 2-4 weeks after initiation of therapy" ¹. The 10.8 mg label puts the same fall at about 21 days ².

In men this is androgen deprivation, the removal of the male hormones a prostate tumor grows on ¹. In trials with more than two years of follow-up, the suppression held for as long as treatment lasted ¹.

In women, the label describes "a similar down-regulation of the pituitary gland," with estradiol, the main estrogen, falling to postmenopausal levels within three weeks ¹. LH and FSH drop to early-cycle levels within four weeks ¹. The label expects a smaller uterus and ovaries and "a regression of sex hormone-responsive tumors, if present" ¹. The effect is reversible: estradiol, LH and FSH return to pretreatment values within 12 weeks of the last implant "in all but rare cases" ¹. This account is the labels', for an approved drug, from studies in people ¹, ².

What does the research show?

The evidence sits at the top tier: FDA approval on the controlled trials each label describes, plus a published long-term follow-up in early breast cancer ¹, ², ⁷. Most of the label trials compared goserelin with surgery or an older drug rather than with placebo ¹.

Studied in men with prostate cancer: in a multicenter controlled trial of 466 men, the tumors were bulky and in or just beyond the gland ¹. Of these, 231 were given goserelin with flutamide and radiation, and 235 radiation alone ¹. Local failure, the cancer returning where it was treated, was 16 percent at four years with the hormonal treatment against 33 percent without ¹. Median disease-free survival, the time half the men lived without the cancer returning, was 4.4 years against 2.6 ¹. Distant metastases showed "a trend toward reduction," 27 percent against 36, that did not reach significance ¹.

Studied in men with advanced prostate cancer: the comparison was with orchiectomy, surgical removal of the testes ¹. In the controlled studies of 242 men on goserelin and 254 after orchiectomy, "the long-term endocrine responses and objective responses were similar between the two treatment arms," and so was survival in a comparative trial ¹. Two further controlled trials randomized 160 men between the two implants ². Testosterone suppression was similar ². PSA, the prostate's blood marker, fell by 94 percent at three months on the larger implant and by 92.5 on the smaller ².

Studied in women with endometriosis: two controlled studies of 411 women on goserelin and 207 on danazol, an older hormone drug, gave six months of treatment ¹. Goserelin "was shown to be as effective as danazol" on pain, tenderness and the size of lesions seen at laparoscopy ¹. A halving or more of the lesions was seen in 63 percent of women on goserelin against 42 on danazol in the first study ¹. In the second study the figures were 62 and 51 percent ¹. The label adds that "the clinical significance of a decrease in endometriotic lesions is not known at this time" ¹.

Periods stopped in 92 and 80 percent of women in the two studies within eight weeks ¹. Symptoms at the end of treatment were reduced by about 84 percent on average ¹. The label says "there is insufficient evidence to determine whether pregnancy rates are enhanced or adversely affected" ¹.

Studied in women with heavy uterine bleeding before ablation: Trial 0022, double-blind, randomized 358 premenopausal women ¹. They received two goserelin implants, 180 women, or two placebo injections, 178, four weeks apart ¹. The lining of the womb measured a median of 1.50 millimeters before surgery on goserelin against 3.55 on placebo ¹.

Six months after ablation, 40 percent (70 of 175) on goserelin had no periods against 26 percent (44 of 171) on placebo, a significant difference ¹. A smaller open-label trial, one in which patients and doctors knew the treatment, compared one implant with two, 40 women per arm ¹. The thinner lining with two implants did not change the rate of absent periods, 24 percent in both ¹.

Studied in women with advanced breast cancer: the SWOG-8692 trial randomized premenopausal women whose tumors carried estrogen or progesterone receptors to goserelin or oophorectomy, surgical removal of the ovaries ¹. On interim data from 124 women, the best objective response, a measured shrinking of the tumor, was 22 percent on goserelin against 12 on surgery ¹. Median time to treatment failure was 6.7 months against 5.5, and median survival 33.2 months against 33.6 ¹. In two uncontrolled series of 228 and 159 women, tumors responded in 36 percent of receptor-positive cases and in 18 percent and 3 of 26 of receptor-negative ones ¹.

Studied in women with early breast cancer, a use outside the US labels: the ZEBRA trial compared goserelin with CMF chemotherapy, a combination of cyclophosphamide, methotrexate and fluorouracil ⁷. Both were given as adjuvant treatment, treatment after surgery to lower the risk of return ⁷. The women were pre- or perimenopausal and their cancer had reached the lymph nodes ⁷.

The survival analysis, published in August 2003, reports a median follow-up of 7.3 years ⁷. In women with estrogen-receptor-positive tumors, goserelin was non-inferior to CMF for overall survival, meaning no worse by the trial's test, and equivalent for disease-free and distant disease-free survival ⁷. In women with receptor-negative disease, goserelin was inferior to CMF on all three measures ⁷. The trial's first report gives 817 women on goserelin and 823 on CMF, 1,640 in all ⁸. The authors concluded that it "offers an effective alternative to CMF chemotherapy" for the receptor-positive group ⁷.

No trial of goserelin for weight, muscle, aging or performance appears in the sources cited here, as of November 10, 2026 ⁷, ¹, ². Every trial above enrolled people with one of the approved conditions, except ZEBRA, which studied early breast cancer after surgery, a use the US labels do not carry ⁷, ¹, ².

What are the side effects?

Hot flashes lead in every population, because the drug removes the sex hormones ¹, ². The labels call the most common events in men "the expected physiological effects from decreased testosterone levels," and in women those of hypoestrogenism, the lack of estrogen ¹, ². In the controlled trials, 242 men on goserelin were compared with 254 who had orchiectomy ¹. Hot flashes were reported by 62 percent against 53, sexual dysfunction by 21 against 15, and decreased erections by 18 against 16 ¹. Lower urinary tract symptoms were reported by 13 percent against 8 ¹.

Surgical complications affected 18 percent of the orchiectomy group, and injection site reactions 3 percent of the goserelin group ¹. On the 10.8 mg implant, 157 men followed from week 12 to week 48 reported hot flashes in 64 percent, general pain in 14 and breast enlargement in 8 ².

In 411 women treated for endometriosis against 207 on danazol, hot flashes (the label's "hot flushes") were reported by 96 percent against 67 ¹. Vaginitis, inflammation of the vagina, was reported by 75 percent against 43, and headache by 75 against 63 ¹. Decreased libido was reported by 61 percent against 44, emotional lability, rapid mood swings, by 60 against 56, and depression by 54 against 48 ¹. In the endometrial-thinning trial's safety table, 180 women on goserelin against 177 treated with placebo, hot flashes (the label's "vasodilatation") were reported by 57 percent against 18 ¹. Headache was reported by 32 percent against 22, and sweating by 16 against 5 ¹.

In 57 women with advanced breast cancer against 55 who had oophorectomy, hot flashes were reported by 70 percent against 47 and tumor flare by 23 against 4 ¹. Bone is the slow cost. After six months of treatment, 109 women showed an average 4.3 percent loss of vertebral bone mineral density ¹. Sixty-six of them re-measured six months after treatment still showed a 2.4 percent loss ¹. Twenty-eight re-measured at 12 months showed a 2.5 percent loss, which the label reads as "a possibility of partial reversibility" ¹.

Post-marketing reports add osteoporosis, decreased bone mineral density and bone fracture in men ¹. The labels' own warnings follow. Both warn of tumor flare: "transient worsening of tumor symptoms may occur during the first few weeks of treatment," which "may include ureteral obstruction and spinal cord compression" ¹, ². Both warn that "hyperglycemia and an increased risk of developing diabetes have been reported in men receiving GnRH agonists" ¹, ². Both warn that "increased risk of developing myocardial infarction, sudden cardiac death and stroke has been reported in association with use of GnRH agonists in men" ¹, ².

Both warn of severe skin reactions including Stevens-Johnson syndrome ¹, ². Both warn that androgen deprivation may prolong the QT interval, a heart rhythm change ¹, ². Both warn of injection site injury "including pain, hematoma, hemorrhage and hemorrhagic shock" ¹, ². The 3.6 mg label adds, for women, that "depression may occur or worsen in women during treatment with GnRH agonists" ¹. It says pregnancy "must be excluded" before treating a benign condition, and that the drug "can cause fetal harm" ¹.

Hypercalcemia, high blood calcium, "has been reported in some prostate and breast cancer patients with bone metastases" ¹. Post-marketing reports include pituitary apoplexy, a syndrome following infarction, a loss of blood supply, of the pituitary gland, mostly within two weeks of the first dose ¹. They also include "psychotic disorders, mood swings, including depression; suicidal ideation and attempt" ¹. Both labels contraindicate goserelin in anyone hypersensitive to GnRH or a GnRH agonist analog ¹, ². Both contraindicate it in pregnancy, except, for the 3.6 mg implant, in the palliative treatment of advanced breast cancer ¹, ².

In sport

Goserelin is prohibited at all times under WADA's 2026 list ⁹. WADA, the World Anti-Doping Agency, names it in section S2.2.1, "Testosterone-stimulating peptides in males," under "gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues (e.g. buserelin, deslorelin, goserelin, histrelin, leuprorelin, nafarelin and triptorelin)" ⁹. That bullet sits in section S2, "peptide hormones, growth factors, related substances, and mimetics," which the list prohibits in and out of competition ⁹.

What JumpstartMD offers

JumpstartMD does not prescribe goserelin. Our peptide library covers it so you have the facts on its FDA status and the evidence, current as of November 10, 2026.

Ready to talk?

Book FREE Consultation

Share your details and a JumpstartMD team member will reach out shortly. Or call 408.478.3496 for your free, no-obligation consultation.

Share your details and a JumpstartMD team member will reach out when we open.

Disclaimer

Compounded medications are not FDA-approved, and FDA does not review their safety, effectiveness, or quality before they are marketed. A licensed clinician decides after an evaluation whether a peptide is appropriate for you, and not every patient will qualify.