Irreversible Effects of Previous Cortisol Excess on Cognitive Functions in Cushing’s Disease

10 04 2010

ResearchBlogging.orgApril 8th is Cushing’s Awareness Day. This day has been chosen as a day of awareness as it is the birthday of Dr. Harvey Cushing, a neurosurgeon, who discovered this illness.

Cushing’s disease is a rare hormone disease caused by prolonged exposure to high levels of the stress hormone cortisol in the blood, whereas Addison’s disease is caused by the opposite: the lack of cortisol. For more background information on both see this previous post. Ramona Bates MD, of Suture for a Living, has written an excellent review (in plain language) about Cushing’s Disease on occasion of Cushing Awareness Day at EmaxHealth.

From this you can learn that Cushing’s disease can be due to the patient taking cortisol-like glucocorticoids, such as prednisone for asthma (exogenous cause), but can also arise because people’s bodies make too much of cortisol itself.  This may be due to a tumor on the pituitary gland, the adrenal gland, or elsewhere in the body.

Symptoms of Cushing’s disease are related to the effects of high levels of cortisol or other glucocorticoids on the immune system, the metabolism and  the brain. Symptoms include rapid weight gain, particularly of the trunk and face (central obesity, “moon face” and buffalo neck), thinning of the skin and easy bruising, excessive hair growth, opportunistic infections, osteoporosis and high blood pressure.

Less emphasized than the clinical features are the often very disabling cognitive deficits and emotional symptoms that accompany Cushing’s disease. Cushing patients may suffer from various psychological disturbances, like insomnia, mood swings, depression and manic depression, and from cognitive decline. Several studies have shown that these glucocorticoid induced changes are accompanied by atrophy of the brain, and in particular of the  hippocampal region, leading to hippocampal volume loss and a profound loss of synapses [2]. This hippocampal loss seems reversible [2], but are neurological and psychological defects also restored? This is far more important to the patient than anatomic changes.

If we listen to Cushing patients, who are “cured” and have traded Cushing’s disease for Addison’s disease, we notice that they feel better after their high levels of cortisol have normalized, but not fully cured (see two examples of ex-Cushing patients with longlasting if not irreversible health) problems in my previous post here. [added 2010-04-17)
To realize how this affects daily life, I recommend to read the photo-blog 365 days with Cushing by Robin (also author of Survive the Journey). Quite a few of her posts deal with the continuous weakness (tag muscle atrophy), tiredness (tag fatigue), problems with (short-term) memory (see tag memory)  or both (like here and here).

Scientifically the question is to which extent ex-Cushing patients score worse than other healthy individuals or chronically ill people and, if so, whether this can be attributed to the previous high levels of glucocorticoids.

A recent study by endocrinologists (and one neurologists) from the Leiden University Medical Center assessed the cognitive functioning of patients  after long-term cure of their Cushing’s disease (caused by a ACTH producing pituitary adenoma, that induces overproduction of cortisol (hypercortisolism) by the adrenals [1]. Previous studies had contradictory outcomes and/or were too small to draw conclusions.

The authors first compared a group of 74 Cushing patients (with a previous pituitary tumor) with matched healthy controls (selected by the patients themselves). Matched means that these controls had the same characteristics as the Cushing patients with respect to gender (male/female: 13/61), age (52 yr) and education.
Cushing patients were on average 13 years in remission and were followed for another 3 years (total 16 yrs follow-up). Cushing’s disease  had been established by clinical signs and symptoms and by appropriate biochemical tests. All patients were treated by transsphenoidal surgery (surgery via the nostrils), if necessary followed by repeat surgery and/or radiotherapy (27%). Cure of Cushing’s disease was defined by normal overnight suppression of plasma cortisol levels after administration of dexamethasone and normal 24-h urinary excretion rates of cortisol. 58% of the patients had at least one form of hypopituitarism (deficiency of one or more hormones) and half of the patients needed hydrocortisone replacement therapy.

Long after their cure, 62% of the Cushing patients reported memory problems, and 47% reported problems in executive functioning. The Hospital Anxiety and Depression Scale (HADS)-score (10.5)  indicated no clinical depression or anxiety. Patients with long-term cure of Cushing’s disease did not perform worse on measures of global cognitive functioning. However, these patients had several other cognitive impairments, mainly in the memory domain.
Only a single test result (FAS, measures verbal mental flexibility and fluency) was significantly different between patients with short and long-term remission.

From direct comparison with healthy controls it is not clear what causes these cognitive alterations in Cushing patients.

Therefore the cognitive function of Cushing patients was compared to that of patients previously treated for non-functioning pituitary macroadenomas (NFMA).
NFMA patients were chosen, because they have undergone similar treatments (transsphenoidal surgery (100%), with repeat surgery and/or radiotherapy (44%) as the Cushing patients. They also shared hypopituitarism and the need for hydrocortisone substitution in half of the cases. NFMA patients, however, have never been exposed to prolonged excess of cortisol.

Cushing patients could not be directly compared to NFMA-patients, because these patient groups differed with regard to age and gender.

Thus Cushing patients were compared to matched healthy controls and NFMA to another set of healthy controls, matched to these NFMA patients (Male/Female: 30/24  and mean age: 61 yr).

To compare Cushing patients with NFMA patients the Z-scores* were calculated for each patient group in relation to their appropriate control group. A general linear model was used to compare the Z-scores.

Overall Cushing patients performed worse than NFMA patients. In the memory domain, patients cured from Cushing’s disease had a significantly lower MQ measured with the Wechsler Memory Scale compared with patients with NFMA in the subscales concentration and visual memory. On the Verbal Learning Test of Rey, patients cured from Cushing’s disease recalled fewer words in the imprinting, the immediate and delayed recall trials. Furthermore, on the Rey Complex Figure, patients with cured Cushing’s disease scored worse on both trials when compared with NFMA patients. In tests measuring executive function, patients cured from Cushing’s disease made fewer correct substitutions on the Letter-Digit Substitution Test and came up with fewer correct patterns on the Figure Fluency Test compared with treated NFMA patients.

These impairments were not merely related to pituitary disease in general and/or its treatment, because these patients with long-term cure of Cushing’s disease also revealed subtle impairments in cognitive function compared with patients previously treated for NFMA. These are most likely caused by the irreversible effects of previous glucocorticoid excess on the central nervous system (because this is the main difference between the two).

Sub-analysis indicated that hypopituitarism was associated with mildly impaired executive functioning** and hydrocortisone dependency** and additional radiotherapy were negatively associated with memory and executive functioning, whereas the duration of remission positively influenced memory and executive functioning.

The main point of criticism, apparently raised during the review process and discussed by the authors, is the presentation of the data without adjustments for multiple comparisons. When more than one test is used, the chance of finding at least one test statistically significant due to chance increases. As the authors point out, however, the positive significant results were not randomly distributed among the different variables. Furthermore, the findings are plausible given the irreversible effects of cortisol excess on the central nervous system in experimental animal and clinical studies.

Although not addressed in this study, similar cognitive impairments would be expected in patients having continuous overexposure to exogenous glucocorticosteroids, like prednison.

* Z-scores: The z score for an item, indicates how far and in what direction, that item deviates from its distribution’s mean, expressed in units of its distribution’s standard deviation. The z score transformation is especially useful when seeking to compare the relative standings of items from distributions with different means and/or different standard deviations (see: http://sysurvey.com/tips/statistics/zscore.htm).

** This makes me wonder whether Addison patients with panhypopituitarism have lower cognitive functions compared to healthy controls as well.

Hattip: Hersenschade door stresshormoon lijkt onomkeerbaar (2010/04/08/) (medicalfacts.nl/)

References

  1. Tiemensma J, Kokshoorn NE, Biermasz NR, Keijser BJ, Wassenaar MJ, Middelkoop HA, Pereira AM, & Romijn JA (2010). Subtle Cognitive Impairments in Patients with Long-Term Cure of Cushing’s Disease. The Journal of clinical endocrinology and metabolism PMID: 20371667
  2. Patil CG, Lad SP, Katznelson L, & Laws ER Jr (2007). Brain atrophy and cognitive deficits in Cushing’s disease. Neurosurgical focus, 23 (3) PMID: 17961025 Freely available PDF, also published at Medscape
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