There is a grain of truth there - but the changes happen at normal pubescent rates, over years, not through any ritual.
Nearly all natural "sex changes" in humans are from (somewhat, mostly, or completely) female to (somewhat, mostly, or completely) male. The handful of known cases of male-to-female changes are not well understood, and are less than 1% of the total.
There are two syndromes that cause female-to-male changes: 5alpha-reductase-2 deficiency (5alpha-RD-2) and 17beta-hydroxysteroid dehydrogenase-3 deficiency (17beta-HSD-3).
It is particularly prevalent in the Dominican Republic, some Pacific Islands, and amongst the Simbari of Papua New Guinea. The rate in the Dominican Republic is 1 in 90, but in the general US population, the combined rate of 5ARD and 17BHDD would not exceed 1 in 40,000, and may be half that.
The head of OII (Organisation Intersex International) has 5ARD.
I'm one of the handful of male-to-female natural changes by the way. Another answer gave my blog URL, which covered several years before things changed, and the 3 years so far afterwards.
All changes of this nature in Humans are not as complete as the sex-reversals commonly found in various species of fish, amphibia and lizards. Some apparently normally female "girls" with 5ARD can masculinise enough to become fathers though.
Gender change in 46,XY persons with 5alpha-reductase-2 deficiency and 17beta-hydroxysteroid dehydrogenase-3 deficiency. by Cohen-Ketternis:
17β-Hydroxysteroid dehydrogenase-3 deficiency: A rare endocrine cause of male-to-female sex reversal by Bertolloni et al
Gynecological Endocrinology, Volume 22, Issue 9 September 2006 , pages 488 - 494.
The sambia “turnim-man”: Sociocultural and clinical aspects of gender formation in male pseudohermaphrodites with 5-alpha-reductase deficiency in Papua New Guinea by Herdt and Davidson