Cortisol

Cortisol is the body's main glucocorticoid hormone, made by the adrenal glands. It follows a daily rhythm — highest in the morning, lowest at night — and its job is survival: raising blood sugar for quick energy, sharpening alertness, dampening inflammation, and helping the body respond to threats. A short spike during a hard workout or a stressful meeting is normal physiology.

On a GLP-1, cortisol's most practical relevance is muscle rather than belly fat. Sustained high cortisol is catabolic, breaking muscle protein down when you're already in a deficit, and the most common everyday driver of elevated cortisol is short sleep. Genuinely pathological excess drives central fat, but ordinary stress does far less than "cortisol belly" marketing implies, and "cortisol-blocker" supplements have no credible evidence. See the guide on cortisol, stress, and weight on a GLP-1.

Related terms

Cushing's syndrome — A condition of persistently excessive cortisol, caused by a hormone-producing tumor or long-term glucocorticoid medication, producing central weight gain, a rounded face, easy bruising, and muscle weakness — distinct from ordinary stress.

Functional hypogonadism — Reduced testosterone in men that results from a reversible cause such as obesity, type 2 diabetes, or sleep apnea rather than damage to the hormonal axis; it typically improves with weight loss and is not an indication for testosterone therapy.

Progestogen — A hormone — natural progesterone or a synthetic progestin — given alongside estrogen in menopausal hormone therapy to protect the lining of the uterus.

Related guides

Cortisol, stress, and weight on a GLP-1: what the connection really is — The "cortisol makes you fat" story is mostly overstated. Genuine cortisol excess like Cushing's clearly drives central fat, but everyday stress does far less — and its most underrated relevance on a GLP-1 is muscle, not belly fat. Here's the honest evidence, why sleep is the cortisol lever you actually control, and why "cortisol-blocker" supplements are marketing, not medicine.

Men's health on a GLP-1: testosterone, fertility, muscle, and the things worth watching — For men, losing weight on a GLP-1 does more than shrink the scale — it can raise testosterone that obesity was quietly suppressing, and unlike testosterone therapy it tends to preserve fertility. Here are the key men's-health angles the research is starting to fill in: the testosterone connection, sexual function and sperm, protecting muscle and bone, cardiovascular benefit, and sleep apnea — plus why the checkup men tend to skip matters more now.

Sleep quality on a GLP-1: why it matters, what changes, and the sleep apnea connection — Sleep is the quiet variable in GLP-1 treatment: short sleep can shift weight loss away from fat and toward muscle, GI side effects and hunger changes can disturb the night, and one GLP-1 medication is now FDA-approved to treat obstructive sleep apnea itself. Here's how sleep stages work, how treatment can affect them, and why protecting deep sleep protects your muscle.