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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Endocrinology · Autoimmune Polyglandular Syndrome Type 2

Understanding Your Diagnosis: APS-2 (Schmidt Syndrome)

At a Glance

Autoimmune Polyglandular Syndrome Type 2 (APS-2), or Schmidt Syndrome, involves Addison's disease occurring with autoimmune thyroid disease or type 1 diabetes. These conditions develop slowly over years. Adrenal insufficiency must be treated before thyroid conditions to prevent an adrenal crisis.

Getting diagnosed with a rare condition like Autoimmune Polyglandular Syndrome Type 2 (APS-2), also known as Schmidt Syndrome, can feel overwhelming [1]. However, understanding the framework of this condition is the first step toward regaining control. APS-2 is not a single disease that attacks everything at once; rather, it is a “syndrome”—a collection of conditions that tend to happen together because of a shared underlying immune system pattern [2].

Understanding the Core Components

APS-2 is defined by the coexistence of primary adrenal insufficiency (Addison’s disease) with at least one other autoimmune endocrine condition [1][2]. The three “pillars” of APS-2 are:

  1. Addison’s Disease: The immune system attacks the adrenal glands, which sit atop the kidneys and produce essential hormones like cortisol (the “stress hormone”) and aldosterone (which balances salt) [3][4].
  2. Autoimmune Thyroid Disease: This includes Hashimoto’s thyroiditis (an underactive thyroid) or, less commonly, Graves’ disease (an overactive thyroid) [2][5].
  3. Type 1 Diabetes Mellitus: The immune system attacks the insulin-producing cells in the pancreas [1].

While these three are the most common, APS-2 can also occasionally involve other autoimmune issues affecting the skin (vitiligo), the stomach (pernicious anemia), or the gonads [6].

Rare but Manageable

APS-2 is considered a rare condition, though its exact prevalence is difficult to pinpoint because it often develops slowly over many years [7]. It is much more common in adults—typically appearing between the ages of 20 and 40—and is more frequently diagnosed in women [8].

Because APS-2 is polygenic (meaning it is caused by a complex interaction of multiple genes), it does not follow a simple inheritance pattern [9]. If you have been diagnosed, your first-degree relatives (parents, siblings, and children) have a higher-than-average risk of developing autoimmune issues, which is covered in the monitoring section [8].

The “Latency Period”: Why You Don’t Need to Panic

One of the most important things to know is that these conditions rarely appear all at once [10]. There is often a significant latency period—years or even decades—between the diagnosis of one component and the appearance of another [10][11].

  • Having one doesn’t mean you have them all: Just because you have Addison’s disease and a thyroid issue does not mean you will definitely develop diabetes [12].
  • Awareness is your best tool: Because doctors know these conditions are linked, they can use “dynamic monitoring”—regular blood tests to catch any new issues long before they become emergencies [13][14].

A Critical Safety Note: The Order of Treatment

If you have both thyroid disease and adrenal insufficiency, the order in which you start medications is vital. Adrenal treatment (steroids like hydrocortisone) must always be stabilized before starting thyroid hormone (levothyroxine) [15][16]. Starting thyroid medication first can speed up your metabolism so much that it puts an unbearable strain on your struggling adrenal glands, potentially triggering a life-threatening adrenal crisis—a sudden, severe lack of cortisol [16][13]. Always ensure your doctor has checked your adrenal function before you begin any new thyroid treatments.

Common questions in this guide

What is APS-2 (Schmidt Syndrome)?
APS-2 is a rare autoimmune condition where the body's immune system attacks multiple endocrine glands. It is officially diagnosed when a person has primary adrenal insufficiency (Addison's disease) along with either autoimmune thyroid disease or type 1 diabetes.
Will I develop all the conditions associated with APS-2 at once?
No. It is very rare for all the conditions to appear at the same time. There is usually a significant latency period, which can be years or decades, between the diagnosis of one component and the appearance of another.
Why is the order of my hormone treatments so important?
If you have both adrenal insufficiency and thyroid disease, you must stabilize your adrenal function with steroid medication before starting thyroid hormone therapy. Starting thyroid treatment first speeds up your metabolism and can trigger a life-threatening adrenal crisis.
What antibodies do doctors test for in APS-2?
Doctors typically run regular blood tests to check for specific autoantibodies, such as 21-hydroxylase, TPO, or GAD65. These tests help identify exactly which glands your immune system might be targeting so they can catch new issues early.
What are the warning signs of an adrenal crisis?
Early warning signs of an adrenal crisis or worsening adrenal insufficiency can include new or increasing fatigue, noticeable darkening of the skin, and intense salt cravings. Always report these symptoms to your endocrinologist immediately.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which specific antibodies have I tested positive for (e.g., 21-hydroxylase, TPO, or GAD65)?
  2. 2.Since I have one component of APS-2, what is the specific schedule for monitoring my other endocrine glands?
  3. 3.Were my cortisol levels confirmed to be normal before starting any thyroid hormone replacement?
  4. 4.What are the early warning signs of an adrenal crisis that I should watch for?

Questions For You

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References

References (16)
  1. 1

    Adrenal crisis in a 14-year-old boy 12 years after hematopoietic stem cell transplantation.

    Penger T, Albrecht A, Marx M, et al.

    Endocrinology, diabetes & metabolism case reports 2018; (2018()).

    PMID: 29899990
  2. 2

    Adrenal crisis and autoimmune polyglandular syndromes.

    Freeland ZK, Lueking R, Tsai-Nguyen G, et al.

    Proceedings (Baylor University. Medical Center) 2017; (30(4)):427-428 doi:10.1080/08998280.2017.11930214.

    PMID: 28966452
  3. 3

    [Just Anorexia?]

    Schafroth C, Oestmann A

    Praxis 2022; (111(12)):707-709 doi:10.1024/1661-8157/a003899.

    PMID: 36102024
  4. 4

    Initiation of levothyroxine in a patient with hypothyroidism inducing adrenal crisis requiring VA ECMO: a tale of preventable disaster.

    Kang MS, Sandhu CS, Singh N, Evans T

    BMJ case reports 2019; (12(8)) doi:10.1136/bcr-2019-230601.

    PMID: 31471362
  5. 5

    Delay in Diagnosis of Autoimmune Polyendocrine Syndrome Type 2 as a Consequence of Misinterpretation of Gastrointestinal Symptoms.

    Gonciarz M, Krogulecki M, Brodowska-Kania D, et al.

    Case reports in gastrointestinal medicine 2022; (2022()):6623020 doi:10.1155/2022/6623020.

    PMID: 35368451
  6. 6

    The "polyglandular crisis" behind recurrent hyponatremia: misdiagnosis of a case of autoimmune polyglandular syndrome type 2 and clinical lessons learned.

    Yan M, Wu H, Deng J, et al.

    Frontiers in immunology 2026; (17()):1744295 doi:10.3389/fimmu.2026.1744295.

    PMID: 41659856
  7. 7

    Atypical Case of Schmidt's Syndrome in a Young Male.

    Abdullah I, Bdaiwi AS, Wess M, Camferdam RR

    Cureus 2022; (14(6)):e26322 doi:10.7759/cureus.26322.

    PMID: 35911265
  8. 8

    Polyglandular syndrome type 2 in a Mexican family and its association with human leukocyte antigen.

    Bermeo-Cabrera J, Reza-Albarrán AA, Granados J, et al.

    Clinical case reports 2019; (7(1)):79-82 doi:10.1002/ccr3.1919.

    PMID: 30656013
  9. 9

    From Genetic Predisposition to Molecular Mechanisms of Autoimmune Primary Adrenal Insufficiency.

    Falorni A, Brozzetti A, Perniola R

    Frontiers of hormone research 2016; (46()):115-32 doi:10.1159/000443871.

    PMID: 27211051
  10. 10

    Autoimmune polyendocrine syndrome type 2 in children: a case report and literature review.

    Liu Y, Wang F, Zhang L, et al.

    BMC pediatrics 2025; (25(1)):351 doi:10.1186/s12887-025-05697-3.

    PMID: 40316945
  11. 11

    Addison's disease in a patient with hypothyroidism: autoimmune polyglandular syndrome type 2.

    Bain A, Stewart M, Mwamure P, Nirmalaraj K

    BMJ case reports 2015; (2015()).

    PMID: 26240101
  12. 12

    A Case of Autoimmune Polyglandular Syndrome Type 2 in Childhood: Unraveling a Rare and Complex Endocrine Puzzle.

    Tayong FM, Gul F, Srujana K, et al.

    Cureus 2025; (17(7)):e87595 doi:10.7759/cureus.87595.

    PMID: 40786351
  13. 13

    Adrenocortical Crisis Triggered by Levothyroxine in an Unrecognized Autoimmune Polyglandular Syndrome Type-2: A Case Report with Review of the Literature.

    Patel DM, Gurumikhani JK, Patel MV, et al.

    Current drug safety 2021; (16(1)):101-106 doi:10.2174/1574886315666200826095842.

    PMID: 32851966
  14. 14

    Autoimmune Polyglandular Syndrome Type 2 With Hurthle Cell Adenoma: A Rare Association.

    Pandya SS, Shah K, Chavda H, Shah K

    Cureus 2025; (17(9)):e92931 doi:10.7759/cureus.92931.

    PMID: 41133083
  15. 15

    Lessons of the month: A challenging presentation of hypopituitarism secondary to an intracerebral aneurysm.

    Mullarkey EM, Iyer A, Ihuoma A

    Clinical medicine (London, England) 2021; (21(2)):e228-e230 doi:10.7861/clinmed.2020-1017.

    PMID: 33762391
  16. 16

    Thyroxine Reveals Addison's Disease: A Case Report.

    Tsinopoulou VR, Kolanis S, Katsarou D, et al.

    Cureus 2025; (17(6)):e86299 doi:10.7759/cureus.86299.

    PMID: 40688962

This page is for informational purposes only and does not replace professional medical advice. Always consult your endocrinologist regarding your specific treatment order and hormone monitoring.

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