
This was inspired by a recent question from @blondfrog. I have Kallmann Syndrome, and it has had a profound effect on my life. Here is my experience with it.
What is Kallmann Syndrome?
Kallmann Syndrome (KS) is a rare genetic reproductive disorder that affects the pituitary system and the hypothalamus. It is a form of hypogonadotropic hypogonadism (HH). During normal puberty, the hypothalamus releases hormones that cause the pituitary to release other hormones which ultimately results in production of testosterone in men and estrogen in women. In people with HH, those initial hormones aren't released, causing either delayed or absent puberty. Kallmann Syndrome differs from regular HH in that the olfactory system is also affected. People with KS have anosmia, or the lack of a sense of smell. They are also generally infertile without special treatment. When untreated, a person develops "eunuchoidal proportions," which means that they have long arms and legs compared to their midsection.
My Story
...I thought I could smell, simply because no one told me otherwise.
In males, KS/HH can be diagnosed in infancy due to the presence of a micropenis and/or undescended testes. When I was born, I had both, so the doctors knew that something was wrong. My medical records don't mention Kallmann Syndrome until I was around 5 or 6 years old, though.
For most of my childhood, I thought I could smell, simply because no one told me otherwise. I was sure that I could smell a scratch 'n' sniff sticker, or the smell of food in the air that people were talking about. It wasn't until I was a teenager that I realized that I really couldn't smell ANYTHING. When I was 18 or 19, I discovered that I couldn't taste flavors, since they are sensed through the olfactory system. It was a huge blow to me, and I lost interest in eating for a period of time.

Before the age of puberty, I was very skinny. I was a very active child. After around age 11 or so, I started gaining weight. Because of my diagnosis, they knew to give me testosterone injections starting at age 13, but I hated them with a passion. I fought my parents tooth and nail, and wouldn't remind my father when he forgot (my parents were divorced then). As a result, my hormone levels were inconsistent throughout my teenage years. I was overweight and suffered bad mood swings. When I was 18, I started giving myself injections regularly and playing sports, and the weight fell off. To this day, I don't know if my reluctance to get the shots regularly in my formative years affected my final penis size or not. Some sources claim that it wouldn't have mattered, some claim that it did. I ended up with a four inch penis and very small testicles (artificial hormone replacement therapy causes the testes to shut down and shrink, because they are "redundant").
My doctor couldn't understand why I didn't want to have a libido. He wasn't trained to help patients cope with the emotional side of a genetic disorder. He seemed to think that if I took my shots, everything would be just fine.
It wasn't until my early twenties that I really started caring about my penis size. I had seen a lot of pornography, thanks to the early internet and parents who weren't as technically savvy as I was. I became extremely depressed and insecure about my body. I convinced myself that no woman would be happy with what I had. It didn't help that I bought a pack of condoms to experiment with, and they were baggy on me. That just made me feel worse. I began to want to kill off my sex drive. I stopped taking my shots for long periods of time, which was effective, but caused more depression and weight gain. My doctor couldn't understand why I didn't want to have a libido. He wasn't trained to help patients cope with the emotional side of a genetic disorder. He seemed to think that if I took my shots, everything would be just fine.

It literally took years of therapy for me to even begin to think about dating.
For years I hated women because of a few "size queens." I hated other men, too, because they were statistically guaranteed to be bigger than me. I hated seeing couples, because I just knew that the girl was with the guy because he had a big penis. It literally took years of therapy for me to even begin to think about dating. I finally had my first relationship at the age of 33, but I still haven't fully experienced sex, and my insecurities are still there underneath. Other people with Kallmann Syndrome have managed to find relationships and get married, so I know deep down that it's possible. I just need to slay my own personal demons.
On a side note, regarding eunuchoidal proportions: possibly due to my sporadic treatment as a teenager, I have long arms and legs. It makes buying clothes that fit a pain in the rear.
I also look younger than my age, which is quite common for people with KS. I am frequently mistaken for being in my 20s, and I was carded in my mid 20s while buying lottery tickets.
Notable People with Kallmann Syndrome
The famous jazz singer "Little" Jimmy Scott had untreated Kallmann Syndrome, which gave him his unique, unbroken high voice.

Brian Brett, a Canadian write, has published a memoir about growing up with Kallmann Syndrome.

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