What is Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)?
Pituitary hyperplasia, an enlargement of the pituitary gland, is a condition often not fully acknowledged but it’s quite common in people with primary hypothyroidism, an underactive thyroid. The enlargement happens because there’s no limiting control on the pituitary and hypothalamus, two critical parts of the brain. The symptoms and imaging results can look similar to a pituitary mass or tumor.
Patients can show signs of hypothyroidism, excessive levels of the hormone prolactin, and even issues with vision if the enlarged pituitary gland puts pressure on the optic nerve. Identifying this condition is vital as the main treatment method is thyroid hormone replacement, not surgery.
What Causes Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)?
In people with primary hypothyroidism, the majority of cases are due to a condition known as chronic autoimmune thyroiditis or Hashimoto’s thyroiditis. This condition involves the body’s immune system attacking the thyroid gland.
Due to this attack on the thyroid, the levels of thyroid hormone in the body are low. This means there is no “braking system” on the hypothalamus – a part of the brain that controls many bodily functions – which in turn sends out a too much of a hormone called thyrotropin-releasing hormone (TRH).
The high levels of TRH lead to an increase in size (known as hyperplasia) of particular cells in the pituitary gland (a pea-sized gland at the base of the brain) that produce thyroid-stimulating hormone (TSH). High levels of TRH can also lead to an increase in size of pituitary cells that produce the hormone prolactin, and this is the reason why these patients have increased prolactin levels.
The increase in size of these specific cells is what ultimately causes enlargement of the pituitary gland. It’s worth noting that these cells, known as thyrotroph cells, make up only 5% to 10% of all cell types in the gland. However, they can lead to significant gland enlargement in those with primary hypothyroidism. The number of these cells can increase by up to 34% in patients with hypothyroidism.
Risk Factors and Frequency for Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
Research has shown that pituitary hyperplasia, or an enlarged pituitary gland, can occur in 25%-81% of individuals with primary hypothyroidism, a condition where your thyroid is not active enough. This was discovered using skull x-rays that revealed an increased volume of the sella turcica, the area of the skull that houses the pituitary gland, in individuals with primary hypothyroidism.
Further studies have suggested a link between the size of the sella turcica (indicating pituitary hyperplasia) and the level of TSH (Thyroid-Stimulating Hormone), a hormone that stimulates the thyroid gland. One study found that 70% of patients with high TSH levels (above 50 IU/mL) had an enlarged pituitary gland.
Signs and Symptoms of Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
Doctors can learn a lot about a patient’s condition through their medical history and a physical examination. Specifically, for conditions related to the pituitary gland, they’ll look for signs of too much or too little function of the gland and its related organs, as well as any complications from an enlarged gland.
When checking for hypothyroidism – a condition where the gland doesn’t produce enough hormones – doctors will look out for symptoms like weight gain, tiredness, intolerance to cold, constipation, dry skin, irregular menstrual cycle in women, and slow growth or obesity in children. Hyperthyroid symptoms like unintentional weight loss, anxiety, tremors, excessive sweating, heat intolerance, and heart palpitations also have to be checked. For women, doctors will ask about irregular menstrual cycles and abnormal milk production since high prolactin levels, which can cause these symptoms, are common in such pituitary-related conditions. Issues with fertility are also a concern. Since an enlarged pituitary gland can cause physical symptoms, doctors will ask about headaches and changes in vision.
Another important aspect of the history is checking for prior diagnoses of endocrine conditions and current medication use. For instance, if a patient is on thyroid medication, it’s important to know if they’re taking it as prescribed. The family medical history, especially any history of autoimmune or endocrine conditions, is also relevant.
The physical examination for these issues is thorough and covers the whole body. Doctors will check the face for certain characteristics like a “peaches and cream” complexion or eyebrow thinning that are associated with hypothyroidism. They’ll also perform a detailed eye exam, checking for issues like swelling or vision field changes. Observing the neck, they’ll look for swelling that could indicate an enlarged thyroid gland. Other signs to look out for include dry skin, weak muscles, slow reflexes, and nail changes like separation of nail from the nail bed or brittle nails. As part of the chest exam, doctors look for unusual heartbeat patterns, soft or barely audible heart sounds, and signs of fluid around the heart or lungs. For children, they’ll measure height and weight, calculate body mass index (BMI), and estimate physical development stages.
Testing for Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
When assessing a patient thought to have primary hypothyroidism, which is an underactive thyroid, doctors examine the patient’s medical history and conduct a thorough physical examination. After that, they carry out various tests to assess the thyroid. They check the levels of TSH (thyroid-stimulating hormone), free T4 (thyroxine), and T3 (triiodothyronine). Typically, in cases of primary hypothyroidism, TSH levels are high and T4 and T3 are low.
One study shows a possible link between very high levels of TSH and the enlargement of the pituitary gland, which is a tiny organ that controls hormone production in your body. If it is suspected that the patient has a TSH-secreting adenoma, a type of tumor that excessively produces TSH, both TSH and free T4 and T3 levels would be high. Conversely, if the clinician suspects hypothyroidism resulting from a pituitary adenoma, or growth, TSH levels would be low or normal, and T4 and T3 would be low.
Once primary hypothyroidism is suspected, extra tests may be required to confirm the diagnosis. These tests include checking for antibodies that may affect thyroid performance. In case a TSH-secreting adenoma is suspected, further tests could be performed to ascertain how the patient’s body responds to a hormone related to TSH.
Also, if the patient has a pituitary lesion or growth, it’s important to check all hormone-producing cells and their associated hormones. These include stress hormones (ACTH and cortisol), reproductive hormones (FSH, LH, testosterone in men and estradiol in women along with their menstrual history), growth-related hormones (IGF-1), and prolactin, a hormone related to breast milk production in women. In those with primary hypothyroidism and pituitary overgrowth, the levels of prolactin could be high due to an overactive pituitary gland.
Doctors would also use imaging tools like an MRI to get a detailed look at the patient’s pituitary gland. However, it can be hard to distinguish between natural pituitary gland growth and a growth such as an adenoma just based on images. Typically, images of pituitary overgrowth show a uniformly enhanced view of the gland with a specific ‘nipple’ sign, where the gland has smooth borders but a distinct protrusion in the middle.
Treatment Options for Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
The main treatment for pituitary gland enlargement due to severe underactive thyroid, or primary hypothyroidism, is thyroid hormone replacement therapy. This therapy aims to treat the hypothyroidism itself. In some cases, especially in children, small and gradually increasing doses of thyroid hormone replacement are used to avoid potential complications associated with the treatment.
After starting the hormone replacement therapy, these patients need to be monitored closely for several reasons. A few patients may experience a rare condition, called pseudotumor cerebri, which could lead to headaches and various vision changes. Furthermore, some may experience a temporary worsening of their vision after the initiation of therapy. This could be due to an imbalance between the production and release of TSH, a hormone that stimulates the thyroid gland, leading to further growth of the pituitary gland. However, these effects usually reverse when TSH levels start to normalize.
It’s important to conduct repeated imaging tests like MRI scans of the pituitary gland to make sure the treatment is working. If the therapy is effective, the pituitary gland should decrease in size. Studies have found that around 85% of patients with pituitary enlargement due to underactive thyroid show a decrease in gland size after starting the hormone therapy. This usually can be noticed after 2 to 4 months. However, if the size of the pituitary gland doesn’t decrease after treatment, the doctor may need to reconsider the diagnosis. In some cases, there might be an underlying adenoma, a type of tumor, which can be suspected if neither the gland size nor TSH levels improve with treatment.
Surgery may be needed in cases where vision is affected or if the size of the pituitary gland continues to increase even after starting hormone replacement therapy. Surgery could help prevent permanent vision loss and help confirm the diagnosis based on tissue analysis.
Therefore, regular follow-ups to monitor symptoms of underactive thyroid, any new symptoms such as headaches or visual changes, and progress in thyroid function due to treatment are critical. Doctors should conduct a detailed visual examination, including assessments of visual fields and a careful examination of the back of the eye, as well as a neurological examination and thyroid lab tests.
What else can Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid) be?
When a doctor is trying to diagnose a mass in the sellar region of the brain, she has to consider several possibilities. These possibilities could include pituitary adenomas (a kind of tumor in the pituitary gland), pituitary hyperplasia (an increase in the size of the pituitary gland), lymphocytic hypophysitis (swelling of the pituitary gland), and more. In children, it can also include craniopharyngiomas (benign brain tumors) and intracranial germ cell tumors (rare brain tumors).
This task is particularly tricky in the specific situation where a patient shows high TSH (thyroid-stimulating hormone) and low thyroid hormone levels, alongside a pituitary mass. In such a case, the patient could either be experiencing pituitary hyperplasia due to primary hypothyroidism (an underactive thyroid), or they may have a non-functioning pituitary adenoma alongside primary hypothyroidism.
That’s not all, a TSH-secreting adenoma – a kind of tumor that secretes TSH – is also a possibility. Though one would generally expect to find high thyroid hormone levels alongside high TSH in this case, there could be simultaneous primary hypothyroidism, which could lead to conflicting results. This is why follow-up imaging and a thorough examination of thyroid hormones is crucial to differentiate and accurately diagnose the problem.
What to expect with Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
The outlook for these patients is generally positive after they receive thyroid hormone replacement therapy. Only a small number need surgery because of the pressure symptoms or an inadequate response to the therapy. Studies show that when these patients receive follow-up care, a majority (85%) see a decrease in the size of their pituitary gland, as seen in repeat MRI scans.
The timeframe for this improvement can vary and is typically reported to range from one week to several months.
Possible Complications When Diagnosed with Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
If the pituitary gland grows too large, it can start to impact the optic chiasm resulting in vision problems. These can include issues with visual fields and eventually, a condition called bilateral hemianopsia where an individual loses half of the field of view, in both eyes. Visual issues can paradoxically get worse when patients begin treatment with a medication called thyroxine. This happens because there’s an imbalance in the production and release of TSH, a hormone controlled by the pituitary gland, which can cause the pituitary to grow even larger.
There are rare complications that can occur with the treatment. Pseudotumor cerebri, a condition where the pressure inside the skull increases for no obvious reason, has been reported in some individual instances when starting levothyroxine. This underlines the need for a thorough follow-up including neurological and fundoscopic (eye) examinations. Empty sella syndrome, a condition where the pituitary gland shrinks or flattens, can also occur due to rapid shrinking of certain cells within the gland after the feedback loop is restored and TRH stimulation is removed with thyroid hormone replacement therapy.
If pituitary gland enlargement goes on for a long time, it can lead to other hormonal deficiencies and eventually, a condition known as hypopituitarism. Pituitary cells growing over time can cause damage to nearby cell types.
The last very rare complication of pituitary enlargement due to primary hypothyroidism is spontaneous ovarian hyperstimulation syndrome. Symptoms can vary in severity and include abdominal discomfort, fluid in the abdomen, electrolyte imbalances, increased levels of creatinine, and respiratory distress. This happens because TSH also has weak FSH activity, possibly stimulating the FSH receptor. Also, when a woman has hypothyroid syndrome, there could be more production of a hormone called estriol, resulting in lower suppression of the release of gonadotrophins compared with estradiol.
Preventing Pituitary Hyperplasia in Primary Hypothyroidism (Untreated Hypothyroid)
If a person has an enlarged pituitary gland due to primary hypothyroidism, their symptoms can vary widely and be unexpected. It’s essential that patients understand the need to consistently attend follow-up appointments. It’s just as important to stick to their prescribed medication schedule. If they notice any new symptoms, especially things like worsening headaches or changes in their vision, they should seek medical help immediately.
Patients need to be aware of any additional tests they may need to undertake before their next appointment. These may include blood tests or imaging scans, which are crucial to ensuring the treatment is working effectively and to confirm the diagnosis. Understanding the importance of these additional tests will help ensure patients receive the highest level of care and treatment.