Unraveling the Complex Relationship Between Growth Hormone and Thyroid Function
In this podcast, we explore the intricate connection between growth hormone and thyroid function, delving into the effects of growth hormone excess and deficiency on thyroid health. Joining me is Dr. Laurence Katznelson, a renowned expert in pituitary disorders and former president of the Pituitary Society.
The Physiology of Growth Hormone and Thyroid Function
Dr. Katznelson explains that growth hormone plays a crucial role in impacting peripheral deiodination of thyroxine (T4) to triiodothyronine (T3). The ambient levels of growth hormone influence this process, which can have significant implications for thyroid physiology. Additionally, growth hormone affects thyroid gland growth, leading to the development of goiters and nodules in patients with acromegaly.
Thyroid Nodules and Cancer in Acromegaly
Studies have shown that patients with acromegaly have a higher prevalence of thyroid nodules, with some reports suggesting that up to 80% of patients have nodules. However, the incidence of thyroid cancer in these patients is unclear, with varying reports in the literature. Dr. Katznelson emphasizes the importance of evaluating thyroid nodules in patients with acromegaly, using a combination of physical examination, ultrasound, and biopsy.
Screening for Acromegaly in Patients with Thyroid Nodules
While the presence of thyroid nodules alone is not sufficient to warrant screening for acromegaly, a combination of nodules and other comorbidities, such as sleep apnea, diabetes, and hypertension, may prompt further evaluation. Dr. Katznelson suggests that clinicians consider obtaining an IGF-1 level in patients with thyroid nodules who also have these comorbidities.
Challenges in Performing Thyroid Surgery in Patients with Acromegaly
Patients with acromegaly often have a thick neck and oropharynx, making intubation and surgery more complicated. Dr. Katznelson emphasizes the importance of careful evaluation and management of these patients, including preoperative assessment by an anesthesiologist and consideration of somatostatin analogs to reduce growth hormone levels.
Impact of Somatostatin Analogs on Thyroid Function
Somatostatin analogs, such as octreotide and lanreotide, can reduce TSH levels and impact peripheral conversion of T4 to T3. Dr. Katznelson notes that these medications can lead to hypothyroidism and emphasizes the importance of monitoring thyroid hormone levels in patients receiving these treatments.
Growth Hormone Deficiency and Thyroid Function
Growth hormone deficiency can impact thyroid function, particularly in adults who acquire the deficiency. Dr. Katznelson explains that growth hormone replacement can enhance peripheral conversion of T4 to T3, potentially leading to hypothyroidism. He recommends monitoring thyroid hormone levels and adjusting levothyroxine doses as needed.
Key Takeaways
Dr. Katznelson emphasizes the importance of monitoring thyroid hormones in patients with growth hormone deficiency and acromegaly. He also stresses the need to evaluate the thyroid gland in patients with acromegaly, using a combination of physical examination, ultrasound, and biopsy. Finally, he highlights the importance of careful management of patients with acromegaly who require thyroid surgery.
Conclusion
In conclusion, the relationship between growth hormone and thyroid function is complex and multifaceted. Clinicians must be aware of the potential effects of growth hormone excess and deficiency on thyroid health and take a comprehensive approach to evaluating and managing these patients.
