There is a clinically established inverse relationship between sex hormone binding globulin (SHBG) and androgenetic alopecia (AGA). Studies have shown that those with AGA have lower circulating levels of SHBG compared to the non-balding controls.

There are several drugs (like oral antiandrogens) that elevate SHBG levels but have a host of side effects that limit their usage on a continuous basis in men.

There are also, however, two health enhancing compounds that elevate SHBG levels while offering additional health benefits and are side effect free. Green Tea Extract elevates SHBG while having the added benefit of reducing estrogen levels, which via an SHBG binding route can upregulate androgen activity. Soy isoflavones have also been shown in several studies to elevate SHBG levels and to be mildly anti-estrogenic.

In addition to a significantly lower incidents of most types of cancer, including prostate cancer and breast cancer, the oriental population whose traditional diet is abundant in soy isoflavones and green tea catechins have a drastically lower overall incidence of androgenetic alopecia and acne compared to the US.

Interestingly, those of Asian origin living in the US have an almost identical incidence of androgen mediated disorders (prostate cancer, BPH, hair loss) as the US general population.
Hormonal Profile in men with premature androgenic alopecia [Article in Czech]
Starka L, Hill M, Polacek V.
Endokrinologicky ustav a IPVZ, Praha, Czech Republic.

Androgenetic alopecia especially that with premature onset can be a cause of serious psychic trauma. As far as the treatment with antiandrogens, inhibitors of 5 alpha-reductase or hair transplantation represents a heavy economic burden for the patient, we tried to exclude other hormonal causes or to find a criterion for the apt candidates for the treatment in 15 young men with premature androgenetic alopecia. Hormonal analysis discovered a significantly lower plasma level of sexual binding globulin (SHBG) and FSH and nearly significantly higher concentration of 17 alpha-hydroxyprogesterone. These data resemble those in the hormonal pattern of women suffering from the syndrome of polycystic ovaries (PCOS). The finding of premature balding as the possible male phenotype hormonal equivalent of polycystic ovaries is in concordance with several pedigree studies in kindreds with PCOS, which have suggested a genetic basis of this syndrome in some families in which balding and pilosity was frequent in male members.
Female androgenic alopecia. The 3 alpha, 17 beta-androstanediol glucuronide/sex hormone binding globulin ratio as a possible marker for female pattern baldness.
De Villez RL, Dunn J.

Twenty-five women fulfilling the criteria for female alopecia, of either the male pattern baldness type or female pattern baldness type, were evaluated for hormone markers to delineate the clinical baldness patterns. Women with a marked increase in the 3 alpha, 17 beta-androstanediol glucuronide/sex hormone binding globulin ratio and low serum sex hormone binding globulin were noted to have female pattern baldness. This pattern of baldness may represent hair loss from the influence of minimal androgen excess on genetically sensitive hair bulbs in the absence of other signs of maximal androgen excess, including hirsutism, acne, or virilism.
Sex hormone-binding globulin and saliva testosterone levels in men with androgenetic alopecia.
Cipriani R, Ruzza G, Foresta C, Veller Fornasa C, Peserico A.

Sex hormone binding globulin (SHBG), plasma testosterone and saliva testosterone were measured in sixty-four men with androgenetic alopecia and in forty males within the same age range without alopecia. There was a significant reduction in SHBG levels in bald men, compared with controls. Plasma testosterone levels were not raised in bald men, but their salivary testosterone levels were significantly higher than in controls.
Dietary isoflavones affect sex hormone-binding globulin levels in postmenopausal women.
Pino AM, Valladares LE, Palma MA, Mancilla AM, Yanez M, Albala C. Instituto De Nutricion y Tecnologia de Los Alimentos, Universidad de Chile, Santiago.

The studies presented in this report were designed to further investigate the causal association between phytoestrogen action and increase in sex hormone-binding globulin (SHBG) levels. Phytoestrogens include isoflavones that bind to estrogen receptors and therefore exert estrogenic action. This study included 20 postmenopausal women that ingested 30 g soy milk daily for 10 weeks. Plasma concentrations of isoflavones and SHBG were measured. Total isoflavones significantly increased from 0.014 +/- 0.01 micromol/L(baseline) to 0.53 +/- 0.19, micromol/L, and paired responses showed that some subjects clearly increased their SHBG levels. The percent change in SHBG showed a positive correlation with phytoestrogen concentration; all women who had circulating phytoestrogen levels above 0.6 micromol/L increased by at least 30% their SHBG values. Results suggest that phytoestrogens may significantly increase SHBG in subjects whose SHBG concentrations are in the low end of the concentration range.
Association of coffee, green tea, and caffeine intakes with serum concentrations of estradiol and sex hormone-binding globulin in premenopausal Japanese women.
Nagata C, Kabuto M, Shimizu H.
Department of Public Health, Gifu University School of Medicine, Japan.

Caffeine intake has been proposed to influence breast cancer risk. Its effect may be mediated by hormonal changes. The relationships between caffeine-containing beverages (coffee, green tea, black tea, oolong tea, and cola) and serum concentrations of estradiol and sex hormone-binding globulin were evaluated in 50 premenopausal Japanese women. Intakes of caffeine and caffeine-containing beverages were assessed by a semiquantitative food-frequency questionnaire. Blood samples were obtained from each woman on Days 11 and 22 of her menstrual cycle. High intakes of caffeinated coffee, green tea, and total caffeine were commonly correlated with increasing sex hormone-binding globulin on Days 11 and 22 of the cycle after controlling for potential confounders [Spearman correlation coefficients (r) ranged from 0.23 to 0.31]. Green tea but not caffeinated coffee intake was inversely correlated with estradiol on Day 11 of the cycle (r = -0.32, p = 0.04). Although the effect of caffeine cannot be distinguished from effects of coffee and green tea, consumption of caffeine-containing beverages appeared to favorably alter hormone levels associated with the risk of developing breast cancer.