A molecule that inhibits or prevents an interaction between a Src family kinase and an androgen receptor or estradiol receptor, for use in preventing or treating a non-cancerous condition in a subject, or for use in preventing or treating a cancerous condition in a subject who is fertile and in whom fertility is to be preserved, wherein the molecule comprises the structure: B j -[(Pro) n -X r -His-Pro-His-Ala-Arg-Ile-Lys] m -R p, or B j -[lys-ile-arg-ala-his-pro-his-x r -(pro) n] m -R p, or a derivative or fragment thereof, wherein B is a first chemical moiety, j is 0 or 1, n is an integer from 1-10, X is any amino acid, r is an integer from 0 to 2, m is an integer from 1 to 3, R is a second chemical moiety, p is 0 or 1, and [lys-ile-arg-ala-his-pro-his-x r -(pro) n] is the retro-inverso peptide of [(Pro) n -X r -His-Pro-His-Ala-Arg-Ile-Lys], and wherein the molecule is a peptide of between 3 and 57 amino acids in length, and wherein the molecule does not reduce or prevent fertility in the subject, wherein the derivative comprises one or more amino acids chemically derivatised by reaction of a functional side group and/or one or more naturally occurring amino acid derivatives of the twenty standard amino acids, and wherein the non-cancerous condition is a reproductive condition such as a gynaecological condition, or is a non-cancerous condition selected from the group consisting of: endometriosis, ovarian cysts, fibroids polyps hyperplasia, neoplasia, anovulatory bleeding and endometrial growth in the scrotum, bladder or prostate, and wherein the cancerous condition is a reproductive condition such as a gynaecological condition, or is a cancerous condition selected from the group consisting of: uterine fibroids, fibroids polyps hyperplasia, ovarian cancer, bladder cancer, cervical cancer, uterine cancer, testicular cancer and prostate cancer. B j -[(Pro) n -X r -His-Pro-His-Ala-Arg-Ile-Lys] m -R p, or B j -[lys-ile-arg-ala-his-pro-his-x r -(pro) n] m -R p, or a derivative or fragment thereof, wherein B is a first chemical moiety, j is 0 or 1, n is an integer from 1-10, X is any amino acid, r is an integer from 0 to 2, m is an integer from 1 to 3, R is a second chemical moiety, p is 0 or 1, and [lys-ile-arg-ala-his-pro-his-x r -(pro) n] is the retro-inverso peptide of [(Pro) n -X r -His-Pro-His-Ala-Arg-Ile-Lys], and wherein the molecule is a peptide of between 3 and 57 amino acids in length, and wherein the molecule does not reduce or prevent fertility in the subject, wherein the derivative comprises one or more amino acids chemically derivatised by reaction of a functional side group and/or one or more naturally occurring amino acid derivatives of the twenty standard amino acids, and wherein the non-cancerous condition is a reproductive condition such as a gynaecological condition, or is a non-cancerous condition selected from the group consisting of: endometriosis, ovarian cysts, fibroids polyps hyperplasia, neoplasia, anovulatory bleeding and endometrial growth in the scrotum, bladder or prostate, and wherein the cancerous condition is a reproductive condition such as a gynaecological condition, or is a cancerous condition selected from the group consisting of: uterine fibroids, fibroids polyps hyperplasia, ovarian cancer, bladder cancer, cervical cancer, uterine cancer, testicular cancer and prostate cancer.