What does the pituitary gland do to your hormones?
Almost every hormone on your lab report was asked for by the pituitary first. It is the size of a pea and it sits at the base of your brain. It tells your thyroid, your adrenal glands and your ovaries or testes how hard to work. When a hormone result looks off, there are always two questions. Is the gland struggling, or is the signal to the gland wrong? You cannot answer that from one number. You need the signal and the response, side by side.
Where it sits and who it listens to
The pituitary hangs just under a part of the brain called the hypothalamus, behind the bridge of your nose. The hypothalamus reads what is going on in your life: light and dark, sleep, food coming in, body weight, stress, illness. It passes instructions down to the pituitary. The pituitary turns those instructions into hormones and releases them into the blood.
So the chain runs brain, pituitary, gland. This is the part I care about most in my work. Your hormones do not start in your ovaries or your thyroid. They start with a brain deciding what the body can afford today.
The signals it sends
TSH goes to the thyroid and asks for thyroid hormone. I covered what moves that number in Issue 024.
ACTH goes to the adrenal glands and asks for cortisol. It follows a daily rhythm, highest in the morning and lowest near midnight.
FSH and LH go to the ovaries or the testes. In women they run the menstrual cycle and the making of estrogen and progesterone. In men they drive testosterone and sperm production. Same two hormones, both sexes.
Prolactin is best known for milk production. It also rises for other reasons, and when it does it quiets FSH and LH.
Growth hormone builds a child's height and in adults helps maintain muscle, bone and how the body handles fat and sugar.
The back part of the pituitary releases two more. One tells the kidneys how much water to keep. The other is oxytocin, which matters in labor and breastfeeding.
How the loop works
Every one of these runs on feedback. The pituitary sends a signal. The gland answers with its hormone. The brain and pituitary sense that hormone in the blood and turn the signal down. When the gland cannot answer, the pituitary asks louder.
This gives you a simple way to read a pair of results. Signal high and hormone low means the gland itself is struggling. Signal low or ordinary and hormone low means the asking is the problem, and the place to look is the pituitary or the brain above it.
When a gland goes quiet, ask whether anyone was calling it.
What changes across a life
In the teens and twenties, the signal to the ovaries is sensitive to energy. Eating too little for the amount you train, fast weight loss, and heavy ongoing stress can turn FSH and LH down, and periods stop. Doctors call this hypothalamic amenorrhea. It matters because low estrogen at that age costs bone. If your periods have stopped for three months and you are not pregnant, see a doctor. If food has become a struggle, say so in that appointment. It changes the care you get.
Hormonal birth control deliberately lowers FSH and LH. That is how it works. Low readings on the pill are expected and tell you nothing about your own cycle.
In perimenopause, the ovaries respond less and less to the signal. Estrogen swings and then falls. The pituitary asks louder, so FSH and LH rise. In the years before the last period, FSH can be high one month and ordinary the next. This is why NICE guidance says not to use an FSH test to diagnose menopause in women over 45 with typical symptoms. The diagnosis is made on your age, your cycle and what you are feeling. Testing is considered for women under 45, and matters most under 40.
In men, testosterone declines slowly from midlife. There is no sudden stop. When testosterone is truly low, LH and FSH say where the problem is. The Endocrine Society guideline recommends confirming low testosterone on repeat fasting morning tests and then measuring LH and FSH. High signals mean the testes are not responding. Low or ordinary signals mean the asking has dropped. Common reasons for that include excess body weight, opioid pain medication, high prolactin, and past or current use of testosterone or anabolic steroids, which switch the signal off. That last one applies to plenty of younger men in gyms.
When the pituitary itself is the issue
Small benign growths on the pituitary are common. By some estimates they show up in about one in ten adults scanned for other reasons, and most never cause a problem. A minority make extra hormone or grow large enough to press on what is around them.
The most frequent hormone producing type makes prolactin. The NIDDK describes the signs: irregular or absent periods, milky discharge from the breasts when you are not pregnant or nursing, low sex drive, erection problems, and trouble conceiving. Some medications also raise prolactin, including certain antipsychotics and some drugs for nausea. So does an underactive thyroid. A high prolactin result needs a calm repeat and a look at your medication list before anyone assumes a tumor.
Steroid medication deserves a mention here. Prednisone and similar drugs act like cortisol, so the pituitary stops sending ACTH and the adrenal glands rest. After weeks or months on them, the system needs time to wake up. Never stop steroid medication suddenly. Tapering is the prescriber's call.
An underactive thyroid can also start at the pituitary. In that case free T4 is low and TSH is low or sits in range. It is uncommon. A TSH run alone will not find it.
What I would do first
Look at your results in pairs. TSH next to free T4. LH and FSH next to estradiol or testosterone. If only half of a pair was run, that is your first question for the doctor.
Write down what you take. Birth control, hormone therapy, steroids in any form, opioid pain medication, testosterone, and supplements. Each of these changes what the pituitary sends, and the person reading your labs needs the list.
For testosterone, ask for the test in the early morning, fasting, and expect it to be repeated before anyone draws a conclusion.
If you still have a cycle, note the day of your cycle on the day of the draw. FSH, LH and estradiol mean different things on day 3 and day 20.
Then look at what the brain is reading. Sleep, enough food, and how often your system gets to stand down. I cannot change your pituitary. I can help you change what it is being told. I do not diagnose, order tests or treat, and when a pattern needs a doctor I say so and refer you.
When to push harder with your doctor
Ask for a referral to an endocrinologist if a hormone is low and its signal is also low or ordinary. That pattern points upstream and deserves a specialist's eye.
Push if your periods stopped before 40, or stopped for three months at any age without an explanation. Push if you have milky breast discharge and are not pregnant or nursing. Push if a man has low testosterone on two morning tests and nobody measured LH, FSH and prolactin.
Tell your doctor about new headaches together with changes in your side vision, or thirst and urination that are suddenly extreme. Those need a workup.
A sudden severe headache with vision changes, vomiting or confusion is an emergency. Go to the emergency room.
FAQ
What does the pituitary gland do?
It makes the signal hormones that tell your thyroid, adrenal glands and ovaries or testes how much to produce. It also makes prolactin and growth hormone and releases the hormone that controls water balance. It takes its instructions from the hypothalamus in the brain.
What are FSH and LH?
They are the two pituitary hormones that direct the ovaries and the testes. In women they run the cycle and rise at menopause. In men they drive testosterone and sperm production.
Why is FSH high in menopause?
The ovaries stop responding and estrogen falls. With less estrogen feeding back, the pituitary sends more FSH. During perimenopause the level swings, so one reading cannot confirm or rule out menopause in a woman over 45.
Can stress affect the pituitary gland?
Yes. The hypothalamus reads stress, sleep and energy intake and adjusts what the pituitary sends. Severe stress, undereating and overtraining can lower the signals to the ovaries or testes. Ordinary daily stress does not damage the gland.
What are the symptoms of a pituitary problem?
They depend on which hormone is affected. Common ones are missed periods, milky breast discharge, low sex drive, erection problems, unusual fatigue, and headaches with loss of side vision. Most of these have more ordinary causes, so the next step is bloodwork with a doctor.
In good health,
Yvette Rose
Sources
- NICE. Menopause: identification and management (NG23).
- Bhasin S et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline, 2018.
- NIDDK. Prolactinoma.
This is general wellness education and not medical advice, diagnosis or treatment. Talk to a qualified professional, especially if you are pregnant, nursing, taking medication or managing a condition.