Fina can contribute to development of gyno, but gyno is not caused by a single hormone.
from
http://www.endotext.org/male/male14/male14.htm
ESTROGEN, GH AND IGF-1, PROGESTERONE, & PROLACTIN
...Estrogen and progesterone act in an integrative fashion to stimulate normal adult female breast development. Estrogen, acting through its ER a receptor, promotes duct growth, while progesterone, also acting through its receptor (PR), supports alveolar development (13). This is demonstrated by experiments in ER a knockout mice which display grossly impaired ductal development, whereas the PR knockout mice possess significant ductal development, but lack alveolar differentiation (25,6).
Although estrogens and progestogens are vital to mammary growth, they are ineffective in the absence of anterior pituitary hormones (13). Thus, neither estrogen alone nor estrogen plus progesterone can sustain breast development without other mediators, such as GH and IGF-1, as confirmed by studies involving the administration of estrogen and GH to hypophysectomized and oophorectomized female rats, which resulted in breast ductal development. The GH effects on ductal growth are mediated through stimulation of IGF-1. This is demonstrated by studies of estrogen and GH administration to IGF-1 knockout rats that showed significantly decreased mammary development when compared to age-matched IGF-1- intact controls. Combined estrogen and IGF-1 treatment in these IGF-1 knockout rats restored mammary growth. (21, 36). In addition, Walden et al. demonstrated that GH-stimulated production of IGF-1 mRNA in the mammary gland itself, suggesting that IGF-1 production in the stromal compartment of the mammary gland acts locally to promote breast development (43). Furthermore, other data indicates that estrogen promotes GH secretion and increased GH levels, stimulating the production of IGF-1, which synergizes with estrogen to induce ductal development...
21. Kleinberg DL, Feldman M, Ruan W: IGF-1: An Essential Factor in Terminal End Bud Formation and Ductal Morphogenesis. Journal of Mammary Gland Biology and Neoplasia 5(1):7-17, 2000.
36. Ruan W, Kleinberg DL: Insulin-like Growth Factor I is Essential for Terminal End Bud Formation and Ductal Morphogenesis during Mammary Development. Endocrinology 140(11): 5075-81, 1999.
43. Walden PD, Ruan W, Feldman M, Kleinberg DL: Evidence that the Mammary Fat Pad Mediated the Action of Growth Hormone in Mammary Gland Development, Endocrinology 139 (2): 659-62, 1998