Hormone Deficiency After Radiation to the Head or Neck — Often Mistaken for Depression

Which Glands Are Affected by Radiation to the Head or Neck?

Two areas matter. The thyroid gland sits inside most neck radiation fields. The pituitary gland and the hypothalamus above it sit inside fields treating brain, skull-base, nasopharyngeal and sinus tumours. Either can quietly under-produce hormones months or years later. The parathyroid glands are involved far less often.

Radiation does not have to hit a tumour in a gland to affect that gland. It only has to pass through it. The thyroid lies in the low front of the neck, directly inside the field used for many laryngeal, pharyngeal and neck-node treatments, and inside the older wide chest and neck fields once used for lymphoma. The pituitary and the hypothalamus sit deep in the midline at the base of the brain, which places them inside the field for a great many brain, skull-base, nasopharyngeal, sinus and orbital treatments, and inside almost every childhood cranial treatment.

The pituitary does not fail all at once, and it does not fail randomly. Long-standing endocrine survivorship teaching, reflected in NCCN survivorship guidance, describes a fairly consistent order: the growth hormone axis is usually affected first, then the sex-hormone axis, then the thyroid-stimulating axis, and the adrenal (cortisol) axis usually last. That order is the single most useful thing on this page, because it explains why one normal blood test does not close the question. A pituitary that tests normally two years after treatment can still be short of something at eight years.

Where a risk needs a number, it should be given as a range and dated. Underactive thyroid function after radiation that includes the thyroid is common — the ranges quoted in oncology and endocrine survivorship guidance sit broadly between roughly one in five and one in two treated patients within about five years, varying with the dose the gland received and how much of it was in the field (range as summarised in NCCN and ASTRO survivorship guidance; indicative, as of August 2026). Pituitary deficits after cranial radiation are reported far less often than that and depend heavily on dose and on how many years have passed. Your own risk is a conversation with your radiation oncologist, not a figure from a page.

Your radiotherapy is delivered at an NABH-accredited partner centre; CION Cancer Clinics coordinates your treatment plan, your oncology team and your care throughout. On this particular late effect that coordination is the whole job. The radiation oncologist knows what was in the field. The endocrinologist interprets the bloods. The family doctor is usually the one who ordered the tiredness workup. When those three do not talk to each other, an ordinary blood test that would have explained everything simply never gets requested.

Is This a Late Effect, or Is the Cancer Back?

Hormone deficiency comes on slowly and affects the whole body: fatigue, feeling cold, weight change, low mood, low libido, dry skin. A recurrence more often shows up locally — a new lump, a growing swelling, focal pain, bleeding, a new neurological change. Neither is settled at home. One blood test separates most of them.

Use the two lists below to decide how fast to act, not to decide what you have. The left column is what an endocrine late effect usually looks like: slow, general, and easy to blame on age or on everything you have been through. The right column is what needs a phone call today, and it includes one genuine emergency that patients on a steroid replacement are specifically warned about.

If anything in the right-hand column applies, contact your treating team immediately or call the CION helpline on 1800 202 8726. If you cannot reach anyone quickly, go to the nearest emergency department. The first entry is worth naming plainly: a body that has lost its cortisol axis cannot mount a stress response to an infection, and that situation is treated as an emergency by every guideline. Anyone taking a prescribed steroid replacement should already have sick-day instructions from their endocrinologist — follow those instructions rather than anything you read here.

And please raise the left-hand column too. Survivors routinely decide their tiredness is not worth mentioning because they are alive and others are not. Every follow-up clinic hears this and none of them agree with it. Fatigue that has a name and a blood test behind it is one of the few late effects that is genuinely straightforward to manage.

Why Is Fatigue and Low Mood After Radiation So Often Read as Depression?

Because the two pictures overlap almost completely. Low energy, flat mood, poor concentration, disturbed sleep, weight change and reduced libido appear in both. After cancer treatment a low mood is easy for everyone to explain as understandable. An underactive thyroid or a failing pituitary axis produces the same picture, and shows up on a blood test.

This is the reason this page exists. A survivor six months out of treatment says they are exhausted, they have put on weight, they feel cold, they have stopped enjoying things and they cannot concentrate. Everybody in the room has a ready explanation: they have been through cancer. The explanation is reasonable, it is compassionate, and it stops the conversation exactly one step before the blood test that would have answered it. Months pass. Sometimes years pass.

The two things are not alternatives. Low mood after cancer treatment is real and common, and it deserves treating on its own terms — that is covered on feeling low after treatment ends. What this page argues is narrower and easier: if radiation passed through your neck or the base of your brain, the endocrine bloods should be part of the workup before a mood diagnosis is settled on, not instead of it and not after a year of it. Two of those tests cost very little and take one appointment.

Nothing here is a reason to stop anything you have been prescribed. If you are taking something for your mood, keep taking it and raise this question with the clinician who prescribed it. Stopping a prescribed treatment on the strength of a web page is a genuinely bad outcome, and it is not what this page is asking for.

One more practical note, because it is usually a family member reading this rather than the survivor. Endocrine change is easier to see from the outside than from the inside. The person living it adapts — they go to bed earlier, they wear an extra layer, they stop making plans, and each step feels sensible. A daughter or a spouse who says “you have not been yourself since about March” is giving the clinic more usable information than any symptom list. Write down when the change started and take that date to the appointment.

Which Tests Do You Need, and How Often?

A thyroid panel — TSH with free T4 — is the core test after any field that included the neck. Where the pituitary or hypothalamus was in the field, a morning cortisol, IGF-1, the sex-hormone bloods and prolactin are added. All of these are blood tests. Frequency is set by your treating team, not by a fixed rule.

The table below is a translation aid. It is there so you can walk into a follow-up appointment and ask a specific question instead of a vague one. It is not a self-testing protocol, and no line in it should be used to order your own investigations or to interpret a result without the clinician who knows your field and your dose.

Notice the fourth row, because it catches people out. When the problem is in the pituitary rather than in the thyroid gland itself, the TSH can look unremarkable while the free T4 is low. A panel that reports only TSH can therefore read as normal in someone who is genuinely short of thyroid hormone. If your radiation field included the base of the brain, it is reasonable to ask that free T4 be reported alongside TSH rather than on its own.

What Should I Actually Do Next?

Six steps, in order. None of them require a specialist appointment to begin, and the first one is the step most survivors have never taken.

1. Get your radiotherapy summary. Ask your centre for the treatment summary that names the sites treated and the dose given. Everything on this page depends on whether the neck, the base of the brain, or both, were in the field.
2. Write down when the change began. A month is enough. “Since about March” is far more useful to a clinician than “for a while now”, and it is often the family who can supply it.
3. Ask for the panel that matches your field. A neck field means TSH with free T4. A field involving the base of the brain means the fuller pituitary panel, with the cortisol drawn in the morning.
4. Ask for an endocrinology referral if anything is abnormal or borderline. Borderline results are the ones most often left unrepeated, and they are the ones that most often move.
5. Keep every report in one place. Photograph each result. A trend across three years answers questions that a single value never will.
6. Put the next check in the calendar before you leave. This is a lifelong surveillance question, not a one-time clearance, and the interval belongs to your treating team.

If you would like a second opinion on what your original plan actually covered, or on whether your current follow-up schedule matches your field, a CION radiation oncologist can review the summary with you. Call 1800 202 8726 or use the form below.

What Happens If a Deficiency Is Found?

The gland damage is not undone. What the endocrinologist does instead is replace what the gland no longer makes, then adjust the dose against repeat blood tests until the level sits where they want it. In many patients the fatigue, the cold intolerance and the low mood improve once the level is corrected.

Replacement is usually taken by mouth, sometimes by injection, and which it is depends entirely on the axis involved. None of it is prescribed from a website, and none of it should be started, stopped or adjusted without the endocrinologist managing it. The follow-up rhythm is the part patients underestimate: bloods after the first weeks, then again after any dose change, then settling to a longer interval once the level is stable. Doses are reviewed again during illness, before surgery, in pregnancy and after a significant weight change, because the requirement genuinely changes in each of those situations.

Two honest caveats. First, replacement is a correction rather than a return to your pre-treatment body — it aims to bring the level into range, and how much of your energy comes back varies from person to person. Second, correcting a low level will not resolve fatigue that has more than one cause, and after cancer treatment fatigue usually does. Sleep, deconditioning, anaemia, pain, mood and the treatment itself all contribute. Structured activity remains one of the more effective things to add alongside it, which is set out on exercise after radiation therapy.

If the adrenal axis is the one involved, ask specifically for sick-day rules and a written emergency plan, and make sure someone at home knows what it says. If the thyroid is the one involved, a fuller explanation of that single gland sits on hypothyroidism after neck radiation. And where a child or teenager was treated, growth and puberty are tracked by a paediatric endocrinologist rather than picked up at an adult follow-up — that pathway is described on growth and height after childhood radiation.

The Other Late Effects That Show Up Years Later

Hormone change rarely arrives on its own. The same fields, the same doses and the same slow timeline produce a handful of other late effects, and they are worth recognising early for exactly the same reason. Bone thinning in particular travels with hormone deficiency, since the sex-hormone and thyroid axes both influence bone.

Get the Fatigue Explained, Not Excused

A free consultation with a CION radiation oncologist, a written second opinion on your original plan, and a follow-up schedule that matches the field you were actually treated in.