What is Testolactone

Although originally approved as a palliative treatment for disseminated or advanced breast cancer, testolactone was removed from the market by the manufacturer in February, 2008.

Testolactone is a first generation, steroid aromatase inhibitor. Testolactone decreases serum estrogen concentrations.

Originally classified as a weak androgen, it was not until 1975 that its potent aromatase inhibition effects were discovered.

Although testolactone is structurally related to testosterone, manifestations of androgenic hormonal activity, including virilism, are not seen with its use. Testolactone is well tolerated with minimal toxicity.

Testolactone was found to be effective in approximately 15% of patients with advanced or disseminated breast cancer as demonstrated by either 1) a measurable decrease in size of all tumor masses, 2) a decrease in size of more than 50% of non-osseous lesions (bone lesions remained static), or 3) an improvement in more than 50% of total lesions while the remainder were static.

Due to a small number of clinical studies demonstrating efficacy in breast carcinoma, testolactone is not considered a first line treatment for breast cancer today. More potent third and fourth generation aromatase inhibitors, with substantially more clinical evidence supporting their use, are available.

Testolactone has been shown to be effective in the treatment of precocious puberty and congenital adrenal hyperplasia, and marginally effective in treating severe male infertility due to decreased testosterone to estradiol ratios.

The FDA initially approved testolactone in 1969.

Brand Name



  • breast cancer
  • congenital adrenal hyperplasia
  • infertility
  • precocious puberty

For the adjunctive, palliative treatment of advanced or disseminated breast cancer in postmenopausal women when hormonal therapy is indicated, or in premenopausal women in whom ovarian function has been terminated

Side Effects

  1. abdominal pain
  2. alopecia
  3. anorexia
  4. diarrhea
  5. edema
  6. elevated hepatic enzymes
  7. erythema
  8. glossitis
  9. hypertension
  10. malaise
  11. nausea
  12. paresthesias
  13. peripheral edema
  14. vomiting

Monitoring Parameters

  • LFTs


  • breast cancer
  • breast-feeding
  • children
  • diabetes mellitus
  • geriatric
  • hepatic disease
  • hypercalcemia
  • postmenopausal females
  • pregnancy
  • renal failure
  • renal impairment
  • substance abuse


  • Abarelix
  • Acarbose
  • Alogliptin
  • Alogliptin; Metformin
  • Alogliptin; Pioglitazone
  • Alpha-glucosidase Inhibitors
  • Canagliflozin
  • Canagliflozin; Metformin
  • Cyclosporine
  • Dapagliflozin
  • Dapagliflozin; Metformin
  • Dapagliflozin; Saxagliptin
  • Darbepoetin Alfa
  • Degarelix
  • Dipeptidyl Peptidase-4 Inhibitors
  • Empagliflozin
  • Empagliflozin; Linagliptin
  • Empagliflozin; Linagliptin; Metformin
  • Empagliflozin; Metformin
  • Epoetin Alfa
  • Ertugliflozin
  • Ertugliflozin; Metformin
  • Ertugliflozin; Sitagliptin
  • Estrogens
  • Glipizide; Metformin
  • Glyburide; Metformin
  • Goserelin
  • Histrelin
  • Incretin Mimetics
  • Insulins
  • Leuprolide
  • Leuprolide; Norethindrone
  • Linagliptin
  • Linagliptin; Metformin
  • Meglitinides
  • Metformin
  • Metformin; Pioglitazone
  • Metformin; Repaglinide
  • Metformin; Rosiglitazone
  • Metformin; Saxagliptin
  • Metformin; Sitagliptin
  • Methoxy polyethylene glycol-epoetin beta
  • Miglitol
  • Nafarelin
  • Pramlintide
  • Saw Palmetto, Serenoa repens
  • Saxagliptin
  • SGLT2 Inhibitors
  • Simvastatin; Sitagliptin
  • Sitagliptin
  • Sulfonylureas
  • Thiazolidinediones
  • Triptorelin
  • Warfarin

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