The Grassy Field Of Anecdotal Evidence
This I saw personally, I speak from direct experience.
My Slow Sex Characteristic Development
I have noted this curious physical manifestation not only in my transsexual acquaintances and friends, but in myself.
Growing up I was always rather delicate overall, and this fact bothered my father especially. When puberty hit, although the rush of male hormones caused a near madness of sexual frustration, as well as hideous acne of the ropey, inch-wide blister sort, my body was exceeding slow to develop definite signs of masculinity - a fact I of course delighted in. I did not develop pubic hair until I was approaching 18, and I got my only upper body hairs, all seven of them (three on the chest, the rest on my chin) at age 20, just shortly before my transition. Indeed the appearance of these hairs helped to precipitate my transition, as they were the last, damning evidence that the Gods were not going to magically correct their mistake with regard to my physical sex, and that hoping and praying every day was not enough.
It might also be noted that my testicles did not descend until I was near kindergarten age...a matter of concern to my parents. This may have given me a strange anatomical benefit before my surgery, for I could still shove my testes up into my body cavity to hide them when I 'tucked' my horrid organs to effectively render them invisible...something I did a lot.
All of these physical anomalies strongly suggest to me that there is often a subtle physical manifestation of transsexuality that may be overlooked or ignored, but is nonetheless present.
I have heard many similar stories from other transsexuals.
Of note about my acne, when I was 14, the condition was so severe that I was prescribed female hormones as part of an experiment to control acne. I qualified because my condition really was quite extreme. I did not entirely understand what this meant at that age, however, which was quite a pity as you will see. Soon after beginning my very low dose regimen of hormones, my acne entirely cleared, and I began feeling happier than I ever had since before the onset of puberty. Indeed my joy was such that the sudden brightening of my increasingly dark mood alarmed my parents somewhat, but ultimately they considered it due to the relief from the acne.
One of the most pathetic mistakes of my life occurred but a few months into the program. I began to notice that a tiny, hard lump had formed in my left breast, like a walnut under the nipple. The right nipple had no such lump, and I became both worried and excited. I was dimly hopeful - and thus excited - that the hormones were going to give me breasts and make me a girl at last, but I felt very skeptical of this because of two reasons: the lump was very hard and tender, and there was one only on the left side. Surely baby breasts should be soft and symmetrical, so I began to imagine tumors and cancer. Eventually I was so frightened that it might be a deadly tumor that I made the pathetic mistake of telling my mother. The doctor took one look: end of hormones.
Of course I now know that this was indeed normal breast development, for I have since grown to fill a D-cup, and during my transition my breasts repeated the exact same pattern: hard lump in the left, followed by a duplicate in the right, hard lumps grow bigger, flatten, become rubber doughnuts under the skin, and gradually melt away as the breasts grow to maturity.
If only I had known, hidden my development, bound myself, and kept my mouth shut. Poor little girl me. Oh well! Things did turn out fine in the end...but I cannot help but imagine the benefits of full hormone treatment that young.