@pappythee1st's HRT temperature claims, fact-checked

What did @pappythee1st actually say?

This is a comedy video, and that matters for how we read it. But buried in the jokes are real claims worth examining. The creator says four and a half years on HRT turned them from someone who "used to always be hot" into someone who is "always cold" and feels like an "icebox." They also claim their body temperature is literally 40 degrees Fahrenheit, that drinking blood temporarily warms them, and that sunlight physically burns them. The temperature sensitivity claim is real. The rest is clearly a vampire bit.

The challenge with comedy health content is that the real claim, that HRT meaningfully changes how you perceive and regulate temperature, gets blurred with obvious fiction. Viewers who skip the punchlines might remember the kernel of truth differently than intended. Worth separating what's grounded from what's a joke.

Does the science back this up?

On the core claim, yes, with important nuance. Estrogen and testosterone both influence thermoregulation, and switching hormonal profiles does alter temperature perception for many people. The evidence is clearest for estrogen's role in hot flashes and thermoregulatory set points.

Estrogen widens the thermoneutral zone, the range of temperatures in which the body doesn't need to actively heat or cool itself. When estrogen drops, that zone narrows, triggering hot flashes. Conversely, when someone assigned male at birth begins feminizing HRT, rising estrogen and falling testosterone can shift temperature regulation in ways that feel dramatic to the individual. Daniilenko et al. (2020, Frontiers in Physiology) and work by Freedman (2014, Menopause) both document estrogen's direct effects on hypothalamic thermoregulation. Testosterone, for its part, tends to raise basal metabolic rate and body heat production. Losing testosterone can make someone feel colder in ambient conditions, particularly in the extremities. A 2019 study by Leinung et al. in Endocrine Practice documented diverse physical changes in transgender women on feminizing HRT, including subjective temperature sensitivity shifts reported by patients.

What did they get wrong (or right)?

They got the general direction right and the specifics absurdly wrong, which is fine for comedy but worth flagging. Feeling colder after starting feminizing HRT is a documented, plausible experience. Credit where it's due.

The claim that their body temperature is "like 40 degrees Fahrenheit" is obviously a joke, but just to be explicit: normal human core temperature runs between 97 and 99 degrees Fahrenheit. A core temperature of 40 degrees Fahrenheit is fatal hypothermia. HRT does not change your actual core body temperature in any clinically meaningful way. It changes your perception of temperature, your thermoneutral zone, and your subjective comfort, not the thermometer reading. The "drinking blood" claim is a vampire gag, not a physiological mechanism. The sunburn sensitivity claim has no known hormonal mechanism either, though some patients on estrogen do report increased skin sensitivity, which is a stretch from "burns in sunlight." The framing conflates subjective thermal perception with objective body temperature, which are genuinely different things.

What should you actually know?

If you're on feminizing HRT and feel colder than you used to, you're not imagining it, and you're not alone. The physiology is real. Estrogen influences the hypothalamus directly, affecting how your body sets and defends its temperature. Falling testosterone reduces heat generated by muscle metabolism. Together, these changes can make the same ambient temperature feel noticeably colder than it did before transition.

What this does not mean is that HRT makes your body temperature dangerous or medically abnormal. Your core temperature stays regulated. What changes is the subjective experience of thermal comfort, the threshold at which you feel hot or cold, and sometimes peripheral circulation, which affects how cold hands and feet feel. These are quality-of-life issues worth discussing with your prescriber, not medical emergencies. If you're experiencing significant cold intolerance after starting HRT, it's worth ruling out thyroid changes, since estrogen can affect thyroid-binding globulin levels and alter how thyroid labs are interpreted. That's a conversation to have with a clinician, not something to self-diagnose from a 30-second Instagram video.