Jaclyn Cave
Naturopath, Sydney

Jaclyn Cave
Naturopath, Sydney

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The Journal

PCOS vs Hypothalamic Amenorrhea: How to Tell the Difference

December 23, 2025

If you have irregular or missing periods, common explanations you may have read about include Polycystic Ovary Syndrome (PCOS) and Hypothalamic Amenorrhea (HA). On the surface, these can both present in a similar fashion - irregular or absent cycles, acne, polycystic ovaries on an ultrasound - however, the underlying drivers are completely different. Mistaking one for the other and using incorrect treatment can delay recovery and make symptoms worse.

Jaclyn Cave, Naturopath
In my opinion, the most efficient way to tell the difference between PCOS and HA is through comprehensive history taking and pathology. Your blood work always holds the clues! Understanding the definitions, similarities, differences, and optimal pathology ranges will help you work with your practitioner to get the right diagnosis and plan.

What is PCOS?

PCOS is a metabolic and endocrine condition driven by androgen excess, often accompanied by insulin resistance and inflammation. Ovulation becomes irregular or stops completely because the ovaries produce an excess of androgens, which disrupts the normal feedback loop within the brain. You can read more about PCOS, how it presents, and how it is diagnosed in my article here.

What is HA?

HA occurs when the hypothalamus (our brain’s hormone control centre) down-regulates reproductive signals due to chronic (real or perceived) stress. This can be due to low caloric intake (whether on purpose or by accident), intense exercise, carbohydrate restriction, or emotional pressure. The body is essentially saying ‘It’s not safe for us to ovulate right now’.

Similarities

Both of these conditions can cause cause:

  • Absent or irregular periods
  • Acne or hair changes
  • Polycystic-looking ovaries on ultrasound (yes, this can happen in HA too!)

This overlap is why misdiagnosis is common - an ultrasound alone certainly isn’t enough and is the least helpful investigation to diagnose both PCOS or HA.

Differences - PCOS vs HA
Jaclyn Cave, Naturopath
Signs and symptoms

PCOS:

  • Irregular or absent periods
  • When periods come they can be normal or heavy
  • Acne, commonly along the jawline
  • Hirsutism (facial/body hair) and/or scalp hair thinning
  • Weight gain or difficulty losing weight
  • Skin tags
  • Acanthosis nigricans
  • Low mood, anxiety, depression

HA:

  • Complete absence of periods for 3+ months
  • Fatigue
  • Cold hands/feet, dry skin
  • Hair loss
  • Anxiety or low mood
  • Low libido
  • Poor sleep
  • Light-headedness or dizziness

Investigations

  1. Cycle day 2/3 pathology. FSH, LH, oestradiol, prolactin, testosterone, androstenedione, DHEAS, SHBG, FAI, fasting insulin.

  2. Progesterone 7 days post-ovulation (typically ‘day 21’ if you ovulate on day 14). To determine if ovulation is occurring.

  3. Thyroid and prolactin. To rule out other causes. Ideally a full thyroid panel (TSH, T3, T4, thyroid antibodies), and cycle day 2/3 prolactin.

  4. A pelvic ultrasound. Part of the traditional diagnostic criteria. Not definitive in determining if PCOS or HA as polycystic ovaries can occur in both.

  5. Bone density (DEXA scan). Relevant if amenorrhea has occurred > 6 months.

 

 

Pathology - PCOS vs HA vs optimal ranges

Jaclyn Cave, Naturopath
The key takeaways from this table are:

→ In PCOS there is a high LH:FSH ratio and elevated androgens
→ In HA there is low FSH, LH, and oestrogen, with normal/low insulin

Note: In a progesterone challenge, women with PCOS typically experience a withdrawal bleed. This is due to sufficient oestrogen levels priming the endometrial lining. In contrast, women with HA usually do not bleed, as their low oestrogen state means there is inadequate endometrial lining to shed. This investigation can assist in differentiating between the two conditions in cases of amenorrhoea.

Diagnosis

HA is primarily a diagnosis of exclusion after ruling out all other causes of absent periods. I expect to find:

  • History of low energy availability (eg under-eating, excessive exercise, high stress)
  • Low FSH/LH, low oestrogen, no withdrawal bleed on progesterone challenge
  • Normal prolactin, thyroid, and brain imaging
  • Other causes for amenorrhoea excluded (pregnancy, PCOS, ovarian insufficiency)

PCOS diagnosis requires two out of the three following criteria to be met:

  1. Irregular or absent periods
  2. Clinical or biochemical signs of high androgens (eg acne, elevated testosterone)
  3. Polycystic ovaries on ultrasound (> 20 per ovary)

--> Other conditions mimicking PCOS must be ruled out - thyroid issues, HA, prolactinoma.

How I can help you

We don’t just treat symptoms here - we dig into root causes via pathology analysis, functional testing, lifestyle and dietary review, and targeted nutritional and herbal therapies. Knowing whether it’s PCOS or HA is essential, as the treatment for one can harm the other. I interpret your blood tests with optimal reference ranges in mind and take your full health picture and history into context. The goal in PCOS and HA is ovulation restoration and optimal hormonal health, long term.

Interested in learning more?

You may find the following articles helpful:


If you’re unsure which one of these conditions fits your picture, please get in touch. I help women decode their hormones every day.

Feel free to ask your questions below, or reach out for one-on-one support. I’d love to help you get your cycles back on track!

Author

Jaclyn Cave
BHSc (Nat), BComm (Soc)
Masters Womens Health Med (UNSW)

References:

Beitl, K., Dewailly, D., Seemann, R., et al. (2022). Polycystic Ovary Syndrome Phenotype D Versus Functional Hypothalamic Amenorrhea With Polycystic Ovarian Morphology: A Retrospective Study About a Frequent Differential Diagnosis. Frontiers in Endocrinology, 13, 904706.
Gordon, C. M., Ackerman, K. E., Berga, et al. (2017). Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology & Metabolism, 102(5), 1413-1439.
Morrison, A. E. (2021). A review of the pathophysiology of functional hypothalamic amenorrhoea in women subject to psychological stress, disordered eating, excessive exercise or a combination of these factors. Clinical Endocrinology, 95(2), 229-238.
Ott, J., Robin, G., Hager, M., & Dewailly, D. (2025). Functional hypothalamic amenorrhoea and polycystic ovarian morphology: a narrative review about an intriguing association. Human Reproduction Update, 31(1), 64-79.
Saadedine, M., Kapoor, E., & Shufelt, C. (2023). Functional Hypothalamic Amenorrhea: Recognition and Management of a Challenging Diagnosis. Mayo Clinic Proceedings, 98(9), 1376-1385.
Teede, H. J., Tay, C. T., Laven, et al. (2023). Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. The Journal of Clinical Endocrinology & Metabolism, 108(10), 2447-2469.

 

 

 

The Journal

PCOS vs Hypothalamic Amenorrhea: How to Tell the Difference

December 23, 2025

If you have irregular or missing periods, common explanations you may have read about include Polycystic Ovary Syndrome (PCOS) and Hypothalamic Amenorrhea (HA). On the surface, these can both present in a similar fashion - irregular or absent cycles, acne, polycystic ovaries on an ultrasound - however, the underlying drivers are completely different. Mistaking one for the other and using incorrect treatment can delay recovery and make symptoms worse.

Jaclyn Cave, Naturopath
In my opinion, the most efficient way to tell the difference between PCOS and HA is through comprehensive history taking and pathology. Your blood work always holds the clues! Understanding the definitions, similarities, differences, and optimal pathology ranges will help you work with your practitioner to get the right diagnosis and plan.

What is PCOS?

PCOS is a metabolic and endocrine condition driven by androgen excess, often accompanied by insulin resistance and inflammation. Ovulation becomes irregular or stops completely because the ovaries produce an excess of androgens, which disrupts the normal feedback loop within the brain. You can read more about PCOS, how it presents, and how it is diagnosed in my article here.

What is HA?

HA occurs when the hypothalamus (our brain’s hormone control centre) down-regulates reproductive signals due to chronic (real or perceived) stress. This can be due to low caloric intake (whether on purpose or by accident), intense exercise, carbohydrate restriction, or emotional pressure. The body is essentially saying ‘It’s not safe for us to ovulate right now’.

Similarities

Both of these conditions can cause cause:

  • Absent or irregular periods
  • Acne or hair changes
  • Polycystic-looking ovaries on ultrasound (yes, this can happen in HA too!)

This overlap is why misdiagnosis is common - an ultrasound alone certainly isn’t enough and is the least helpful investigation to diagnose both PCOS or HA.

Differences - PCOS vs HA
Jaclyn Cave, Naturopath
Signs and symptoms

PCOS:

  • Irregular or absent periods
  • When periods come they can be normal or heavy
  • Acne, commonly along the jawline
  • Hirsutism (facial/body hair) and/or scalp hair thinning
  • Weight gain or difficulty losing weight
  • Skin tags
  • Acanthosis nigricans
  • Low mood, anxiety, depression

HA:

  • Complete absence of periods for 3+ months
  • Fatigue
  • Cold hands/feet, dry skin
  • Hair loss
  • Anxiety or low mood
  • Low libido
  • Poor sleep
  • Light-headedness or dizziness

Investigations

  1. Cycle day 2/3 pathology. FSH, LH, oestradiol, prolactin, testosterone, androstenedione, DHEAS, SHBG, FAI, fasting insulin.

  2. Progesterone 7 days post-ovulation (typically ‘day 21’ if you ovulate on day 14). To determine if ovulation is occurring.

  3. Thyroid and prolactin. To rule out other causes. Ideally a full thyroid panel (TSH, T3, T4, thyroid antibodies), and cycle day 2/3 prolactin.

  4. A pelvic ultrasound. Part of the traditional diagnostic criteria. Not definitive in determining if PCOS or HA as polycystic ovaries can occur in both.

  5. Bone density (DEXA scan). Relevant if amenorrhea has occurred > 6 months.

 

 

Pathology - PCOS vs HA vs optimal ranges

Jaclyn Cave, Naturopath
The key takeaways from this table are:

→ In PCOS there is a high LH:FSH ratio and elevated androgens
→ In HA there is low FSH, LH, and oestrogen, with normal/low insulin

Note: In a progesterone challenge, women with PCOS typically experience a withdrawal bleed. This is due to sufficient oestrogen levels priming the endometrial lining. In contrast, women with HA usually do not bleed, as their low oestrogen state means there is inadequate endometrial lining to shed. This investigation can assist in differentiating between the two conditions in cases of amenorrhoea.

Diagnosis

HA is primarily a diagnosis of exclusion after ruling out all other causes of absent periods. I expect to find:

  • History of low energy availability (eg under-eating, excessive exercise, high stress)
  • Low FSH/LH, low oestrogen, no withdrawal bleed on progesterone challenge
  • Normal prolactin, thyroid, and brain imaging
  • Other causes for amenorrhoea excluded (pregnancy, PCOS, ovarian insufficiency)

PCOS diagnosis requires two out of the three following criteria to be met:

  1. Irregular or absent periods
  2. Clinical or biochemical signs of high androgens (eg acne, elevated testosterone)
  3. Polycystic ovaries on ultrasound (> 20 per ovary)

--> Other conditions mimicking PCOS must be ruled out - thyroid issues, HA, prolactinoma.

How I can help you

We don’t just treat symptoms here - we dig into root causes via pathology analysis, functional testing, lifestyle and dietary review, and targeted nutritional and herbal therapies. Knowing whether it’s PCOS or HA is essential, as the treatment for one can harm the other. I interpret your blood tests with optimal reference ranges in mind and take your full health picture and history into context. The goal in PCOS and HA is ovulation restoration and optimal hormonal health, long term.

Interested in learning more?

You may find the following articles helpful:


If you’re unsure which one of these conditions fits your picture, please get in touch. I help women decode their hormones every day.

Feel free to ask your questions below, or reach out for one-on-one support. I’d love to help you get your cycles back on track!

Author

Jaclyn Cave
BHSc (Nat), BComm (Soc)
Masters Womens Health Med (UNSW)

References:

Beitl, K., Dewailly, D., Seemann, R., et al. (2022). Polycystic Ovary Syndrome Phenotype D Versus Functional Hypothalamic Amenorrhea With Polycystic Ovarian Morphology: A Retrospective Study About a Frequent Differential Diagnosis. Frontiers in Endocrinology, 13, 904706.
Gordon, C. M., Ackerman, K. E., Berga, et al. (2017). Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology & Metabolism, 102(5), 1413-1439.
Morrison, A. E. (2021). A review of the pathophysiology of functional hypothalamic amenorrhoea in women subject to psychological stress, disordered eating, excessive exercise or a combination of these factors. Clinical Endocrinology, 95(2), 229-238.
Ott, J., Robin, G., Hager, M., & Dewailly, D. (2025). Functional hypothalamic amenorrhoea and polycystic ovarian morphology: a narrative review about an intriguing association. Human Reproduction Update, 31(1), 64-79.
Saadedine, M., Kapoor, E., & Shufelt, C. (2023). Functional Hypothalamic Amenorrhea: Recognition and Management of a Challenging Diagnosis. Mayo Clinic Proceedings, 98(9), 1376-1385.
Teede, H. J., Tay, C. T., Laven, et al. (2023). Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. The Journal of Clinical Endocrinology & Metabolism, 108(10), 2447-2469.